JP2011138407A - Apparatus, method and program for transmitting and receiving mail - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mail transmitting and receiving apparatus, a mail transmitting and receiving method and a mail transmitting and receiving program that can prevent leakage of information transmitted and received during mail transmission and reception. <P>SOLUTION: A destination mail server is connected if an effective server information storage part storing combinations of name server specification information specifying a name server and mail server specification information specifying a mail server used in a network environment accessing the name server stores the combination of name server specification information obtained from a name server accessible in the network where the apparatus belongs and mail server specification information about the destination mail server. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a mail transmission / reception device, a mail transmission / reception method, and a mail transmission / reception program.

  Conventionally, a network using VPN (Virtual Private Network) has been used. For example, a company or the like may use a VPN when accessing an in-house intranet via the Internet. As a result, a terminal device used by an employee or the like can be connected to the company intranet using the VPN from outside the company. Even when such a terminal device is placed in an external Internet environment, for example, it is possible to send and receive e-mails in an intranet environment within the company.

Special table 2008-532133

  However, the above prior art has a problem that information transmitted / received at the time of mail transmission / reception may be leaked. Specifically, when sending and receiving e-mail, a terminal device in an intranet generally sends a plain text ID, password, mail text, etc. to a mail server with respect to a mail server built in the intranet. Send. The reason for transmitting plaintext information in this way is that security is ensured in the intranet.

  Here, for example, the user may not be aware that the connection to the intranet has been disconnected even though the connection to the intranet is not established due to disconnection of the VPN line or the like. Further, for example, there is a case where the user mistakenly recognizes that the user is connected to the intranet even though the user is not connected to the intranet. In such a situation, the user may perform a mail transmission / reception operation similar to the mail transmission / reception operation performed in the intranet environment even in the Internet environment. In such a case, the terminal device used by the user transmits the plaintext ID, password, mail text, etc. to the Internet environment. For example, when a malicious mail server exists in the Internet environment, the ID, password, mail text, and the like are known to the mail server.

  In recent years, in order to prevent a user from sending an e-mail to an incorrect destination, there is a technique for displaying a warning screen for confirming a destination address when mail is transmitted from the intranet to the outside of the intranet. Are known. Also, in order to prevent forgetting to attach attachments to e-mails, a warning screen is displayed when there is no attachment attached even though there is a character string indicating “attachment” in the transmission text. Display technology is also known. However, even if such a technique is used, the above-described problem relating to information leakage cannot be solved.

  The disclosed technology has been made in view of the above, and an object thereof is to provide a mail transmission / reception apparatus, a mail transmission / reception method, and a mail transmission / reception program capable of preventing leakage of information transmitted and received during mail transmission / reception. .

  The mail transmitting / receiving apparatus disclosed in the present application includes a combination of name server specifying information for specifying a name server and mail server specifying information for specifying a mail server used in a network environment for accessing the name server. To remember. The mail transmission / reception apparatus has an acquisition unit that acquires name server specifying information of the name server from a name server to be accessed in the network to which the mail transmission / reception apparatus belongs. The mail transmitting / receiving apparatus determines whether the combination of the name server specifying information acquired by the acquiring unit and the mail server specifying information of the communication destination mail server is stored in the effective server information storage unit. 1 determination unit. If the first determination unit determines that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the mail transmitting / receiving device It has a connection part that does not connect to the destination mail server. When the first determination unit determines that the combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit, the connection unit Connect to the destination mail server.

  According to one aspect of the mail transmitting / receiving apparatus disclosed in the present application, it is possible to prevent leakage of information transmitted and received during mail transmission / reception.

FIG. 1 is a block diagram illustrating a configuration example of the mail transmission / reception apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a configuration example of a network according to the second embodiment. FIG. 3 is a block diagram illustrating a configuration example of the user terminal device according to the second embodiment. FIG. 4 is a block diagram illustrating a configuration example of the storage unit and the mail transmission / reception unit illustrated in FIG. 3. FIG. 5 is a diagram illustrating an example of the valid server information storage unit. FIG. 6 is a diagram illustrating an example of the candidate server information storage unit. FIG. 7 is a diagram illustrating an example of the invalid server information storage unit. FIG. 8 is a diagram illustrating an example of an inquiry screen whose display is controlled by the inquiry unit. FIG. 9 is a diagram illustrating an example of an inquiry screen whose display is controlled by the inquiry unit. FIG. 10 is a diagram illustrating an example of a warning screen whose display is controlled by the inquiry unit. FIG. 11 is a flowchart illustrating the mail transmission / reception processing procedure performed by the user terminal device according to the second embodiment. FIG. 12 is a flowchart illustrating a determination processing procedure by the determination unit. FIG. 13 is a block diagram illustrating a configuration example of a user terminal device according to the second embodiment. FIG. 14 is a diagram illustrating a computer that executes a mail transmission / reception program.

  Embodiments of a mail transmission / reception apparatus, a mail transmission / reception method, and a mail transmission / reception program disclosed in the present application will be described below in detail with reference to the drawings. The mail transmitting / receiving apparatus, the mail transmitting / receiving method, and the mail transmitting / receiving program disclosed in the present application are not limited to the embodiment.

  First, the configuration of the mail transmitting / receiving apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration example of the mail transmission / reception apparatus according to the first embodiment. A mail transmission / reception apparatus 100 shown in FIG. 1 is an apparatus for transmitting / receiving an electronic mail, and is incorporated in, for example, a personal computer. In the example illustrated in FIG. 1, the mail transmission / reception device 100 communicates with the name server 10 and the mail server 20.

  The name server 10 holds an IP (Internet Protocol) address in association with the host name of the server. For example, when the name server 10 receives a host name from the mail transmitting / receiving apparatus 100, the name server 10 transmits an IP address corresponding to the host name to the mail transmitting / receiving apparatus 100.

  The mail server 20 relays electronic mail transmitted and received between information processing apparatuses. For example, the mail server 20 transmits an electronic mail received from the mail transmitting / receiving apparatus 100 to an information processing apparatus (not shown) or another mail server. Further, for example, the mail server 20 transmits an e-mail received from an information processing apparatus (not shown) or another mail server to the mail transmitting / receiving apparatus 100.

  As shown in FIG. 1, the mail transmitting / receiving apparatus 100 includes a valid server information storage unit 110, an acquisition unit 120, a determination unit 130, and a connection unit 140. The effective server information storage unit 110 stores a combination of name server specifying information for specifying a name server and mail server specifying information for specifying a mail server used in a network environment for accessing the name server. The “name server specifying information” mentioned here indicates, for example, the host name and IP address of the name server, and the “mail server specifying information” indicates, for example, the host name and IP address of the mail server. .

  The acquisition unit 120 acquires name server specifying information of the name server from the name server to be accessed in the network to which the mail transmitting / receiving apparatus 100 belongs. In the example illustrated in FIG. 1, for example, when the mail transmission / reception device 100 performs transmission / reception of an email, the acquisition unit 120 receives the name server specifying information of the name server 10 and the mail server of the mail server 20 from the name server 10. Get specific information.

  The determination unit 130 determines whether or not the combination of the name server identification information acquired by the acquisition unit 120 and the mail server identification information of the mail server 20 is stored in the valid server information storage unit 110.

  The connection unit 140 does not connect to the mail server 20 when the determination unit 130 determines that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit 110. In such a case, the mail transmission / reception apparatus 100 does not perform transmission / reception of electronic mail using the mail server 20.

  On the other hand, the connection unit 140 connects to the mail server 20 when the determination unit 130 determines that the combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit 110. In such a case, the mail transmission / reception apparatus 100 transmits / receives an electronic mail using the mail server 20.

  As described above, the mail transmitting / receiving apparatus 100 according to the first embodiment acquires the name server specifying information of the name server 10 when transmitting / receiving an electronic mail. Then, the mail transmitting / receiving apparatus 100 determines whether or not the combination of the acquired name server specifying information and the mail server specifying information of the destination mail server 20 is stored in the valid server information storage unit 110. In other words, the mail transmitting / receiving apparatus 100 according to the first embodiment determines whether or not the communication destination mail server 20 is a mail server used in the network to which the apparatus belongs, when transmitting and receiving electronic mail. Then, when the mail server 20 is a mail server used in a network to which the mail apparatus 20 belongs, the mail transmission / reception apparatus 100 transmits / receives an e-mail using the mail server 20. Thereby, since the mail transmission / reception apparatus 100 communicates with the mail server 20 determined to be valid, it is possible to prevent leakage of information transmitted and received during mail transmission / reception.

  More specifically, in general, an information processing apparatus such as a server or a personal computer has different name servers to be accessed depending on a network to which the apparatus belongs. For example, even when the information processing device “X” belonging to the Internet environment accesses the name server 10X, the information processing device “Y” belonging to the intranet environment accesses a name server 10Y different from the name server 10X.

  The mail transmission / reception device 100 according to the first embodiment acquires information on the network to which the device itself belongs by acquiring name server specifying information of the name server 10 from the name server 10 to be accessed. Then, the mail transmitting / receiving apparatus 100 determines whether the combination of the name server specifying information and the mail server specifying information of the mail server 20 is stored in the valid server information storage unit 110, thereby validating the mail server 20. Gender can be determined.

  Here, when the mail transmitting / receiving apparatus 100 is the information processing apparatus “X”, the mail transmitting / receiving apparatus 100 transmits / receives an electronic mail via the mail server 20X, and when the information processing apparatus is “Y”, It is assumed that electronic mail is transmitted / received via the mail server 20Y. Further, the valid server information storage unit 110 stores a combination of the name server specifying information of the name server 10X and the mail server specifying information of the mail server 20X. The valid server information storage unit 110 stores a combination of name server specifying information of the name server 10Y and mail server specifying information of the mail server 20Y.

  In such a situation, it is assumed that the mail transmitting / receiving apparatus 100 is connected to the Internet environment, and an operation for transmitting / receiving an electronic mail via the mail server 20X is performed by a user. In such a case, the mail transmitting / receiving apparatus 100 stores the combination of the name server specifying information of the name server 10X and the mail server specifying information of the mail server 20X in the valid server information storage unit 110. Send and receive e-mail.

  On the other hand, the mail transmitting / receiving apparatus 100 is connected to the Internet environment as in the above example, but it is assumed that an operation for transmitting / receiving electronic mail is performed via the mail server 20Y. In such a case, since the combination of the name server specifying information of the name server 10X and the mail server specifying information of the mail server 20Y is not stored in the valid server information storage unit 110, the mail transmitting / receiving apparatus 100 does not pass through the mail server 20Y. Do not send or receive email.

  That is, in the above example, when the mail transmitting / receiving apparatus 100 belongs to the Internet environment, the mail transmitting / receiving apparatus 100 can be controlled not to access the mail server 20Y used in the intranet environment. For example, it is assumed that the mail transmitting / receiving apparatus 100 has a specification for transmitting plaintext information to the mail server 20Y in the intranet. In such a case, the mail transmission / reception apparatus 100 transmits plaintext information to the Internet even when a mail transmission / reception operation similar to the mail transmission / reception operation performed in the intranet environment is performed despite being connected to the Internet environment. Do not send to the environment. Therefore, even when a malicious mail server exists in the Internet environment, the mail transmitting / receiving apparatus 100 does not transmit plaintext information to the mail server. For this reason, the mail transmitting / receiving apparatus 100 according to the first embodiment can prevent leakage of information transmitted and received during mail transmission / reception.

  Next, an example in which the mail transmitting / receiving apparatus disclosed in the present application is applied to a network connectable to an intranet using VPN will be described. In the second embodiment, an e-mail transmission process will be mainly described as an example. However, the mail transmitting / receiving apparatus disclosed in the present application can also be applied to the case of performing an e-mail receiving process.

[Example of Network Configuration in Embodiment 2]
First, the configuration of the network in the second embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating a configuration example of a network according to the second embodiment. As shown in FIG. 2, a DNS (Domain Name System) server 11 and an SMTP (Simple Mail Transfer Protocol) server 21 are installed in the intranet environment in the network 1. In the Internet environment in the network 1, a DNS server 12 and an SMTP server 22 are installed.

  The user terminal device 200a shown in FIG. 2 is connected to the intranet from the Internet environment using VPN. The user terminal device 200a accesses the DNS server 11 when acquiring the host name or IP address of a predetermined information processing device. Further, the user terminal device 200a accesses the SMTP server 21 when transmitting an e-mail. Note that the user terminal device 200a accesses the DNS server 12 and the SMTP server 22 when not connected to the intranet by the VPN.

  The user terminal device 200b shown in FIG. 2 is connected to the Internet. The user terminal device 200b accesses the DNS server 12 when acquiring the host name or IP address of a predetermined information processing device. In addition, the user terminal device 200b accesses the SMTP server 22 when transmitting an electronic mail.

  The user terminal devices 200a and 200b generally hold the IP address of the DNS server to be accessed and the host name or IP address of the SMTP server to be accessed. For example, the user terminal device 200 a holds the IP addresses of the DNS servers 11 and 12 and the host names of the SMTP servers 21 and 22. For example, the user terminal device 200b holds at least the IP address of the DNS server 12 and the host name or IP address of the SMTP server 22.

  Then, for example, the user terminal device 200a transmits an e-mail to the SMTP server 21 or the SMTP server 22 in accordance with a user operation. Here, when the user erroneously recognizes that the user is connected to the intranet even though the user terminal is not connected to the intranet, the user terminal device 200a sends an e-mail to the SMTP server 21 from the user. There is a risk of accepting an operation to transmit. When receiving such an operation, the user terminal device 200a determines whether or not the SMTP server 21 is used in the Internet environment to which the user device currently belongs before performing the process of transmitting an e-mail to the SMTP server 21. Then, the user terminal device 200a determines whether or not to send an e-mail based on the determination result.

[Configuration Example of User Terminal Device According to Second Embodiment]
Next, the configuration of the user terminal device according to the second embodiment will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration example of the user terminal device according to the second embodiment. Note that the user terminal device 200 illustrated in FIG. 3 is an information processing device such as a personal computer, for example, and corresponds to the user terminal devices 200a and 200b illustrated in FIG. As illustrated in FIG. 3, the user terminal device 200 includes an input unit 210, an output unit 220, a storage unit 230, a communication control unit 240, an IF (Interface) unit 250, and a mail transmission / reception unit 260.

  The input unit 210 is an input device for inputting various information and operation instructions, and is, for example, a keyboard or a mouse. The output unit 220 is an output device that outputs various types of information, and is, for example, a display or a speaker.

  The storage unit 230 is a storage device that stores various types of information. The storage unit 230 stores name server specifying information, mail server specifying information, and the like as various types of information used for the mail transmitting / receiving unit 260 described later. Various information stored in the storage unit 230 will be described later.

  The communication control unit 240 controls communication performed with an external device. For example, the communication control unit 240 controls communication performed between the user terminal device 200 and the DNS server 11 or 12, communication performed between the user terminal device 200 and the SMTP server 21 or 22, and the like. The IF unit 250 is, for example, a physical port to which a cable or the like is connected.

  The mail transmission / reception unit 260 performs electronic mail transmission / reception processing, and corresponds to, for example, a “mailer” used by a user. The mail transmission / reception unit 260 includes a mail monitoring unit 270 and a network monitoring unit 280. The mail monitoring unit 270 monitors whether or not an electronic mail is transmitted, and determines whether or not an electronic mail may be transmitted to the SMTP server 21 or 22. The network monitoring unit 280 monitors the state of the network to which the user terminal device 200 belongs.

  The communication control unit 240 and the mail transmission / reception unit 260 described above are, for example, integrated circuits such as an application specific integrated circuit (ASIC) and a field programmable gate array (FPGA). The storage unit 230 described above is, for example, a semiconductor memory element such as a random access memory (RAM), a read only memory (ROM), or a flash memory, or a storage device such as a hard disk or an optical disk.

  Next, the configuration of the storage unit 230 and the mail transmission / reception unit 260 illustrated in FIG. 3 will be described with reference to FIG. FIG. 4 is a block diagram illustrating a configuration example of the storage unit 230 and the mail transmission / reception unit 260 illustrated in FIG. 3. As illustrated in FIG. 4, the storage unit 230 includes a valid server information storage unit 231, a candidate server information storage unit 232, an invalid server information storage unit 233, and a log storage unit 234.

  The valid server information storage unit 231 stores a combination of name server specifying information for specifying a DNS server and mail server specifying information for specifying an SMTP server used in a network environment for accessing the DNS server. In addition, the valid server information storage unit 231 stores the host name of the user terminal device that is permitted to perform mail transmission under such a network environment, the source mail address of the email that is permitted to be transmitted, and the like. In other words, the valid server information storage unit 231 stores, as a white list, conditions under which the user terminal device 200 is permitted to transmit an e-mail.

  FIG. 5 shows an example of the valid server information storage unit 231. As shown in FIG. 5, the effective server information storage unit 231 includes “DNS host name”, “DNS IP address”, “SMTP host name”, “SMTP IP address”, “host name”, “sender address”, “ It has an item such as “expiration date”.

  “DNS host name” indicates the host name of the DNS server. “DNS IP address” indicates the IP address of the DNS server indicated by the corresponding “DNS host name”. “SMTP host name” indicates the host name of the SMTP server used in the network environment for accessing the DNS server indicated by the corresponding “DNS host name”. “SMTP IP address” indicates the IP address of the SMTP server indicated by the corresponding “SMTP host name”. “Host name” indicates the host name of the information processing apparatus that transmits the electronic mail. “Sender address” indicates an e-mail transmission source mail address. The “expiration date” indicates the expiration date of various types of information stored in the valid server information storage unit 231. Of the various types of information stored in the valid server information storage unit 231, “*” indicates arbitrary information.

  For example, the first line of the effective server information storage unit 231 shown in FIG. 5 is a DNS server whose host name is “dns.xxx.co.jp” and whose IP address is “10.xxx.192.2”. Indicates the conditions under which e-mail transmission is permitted in a network environment that accesses. Specifically, the first line of the valid server information storage unit 231 shown in FIG. 5 has a host name “smtp.xxx.co.jp” and an IP address “10.xxx.192.5”. Indicates that sending an e-mail to an SMTP server is permitted. The first line of the effective server information storage unit 231 shown in FIG. 5 indicates that mail transmission by a user terminal device having a host name “zzz.yyy.xxx.co.jp” is permitted. Further, the first line of the valid server information storage unit 231 shown in FIG. 5 indicates that an e-mail with a source mail address “foo@xxx.co.jp” is permitted to be transmitted to the SMTP server. Indicates. The first line of the valid server information storage unit 231 shown in FIG. 5 indicates that various conditions are valid until “September 30, 2009”. In the IP address shown in FIG. 5, the “xxx” portion indicates a numerical value with a maximum of three digits.

  The candidate server information storage unit 232 stores a combination of name server specifying information for specifying a DNS server and mail server specifying information for specifying an SMTP server candidate used in a network environment for accessing the DNS server. Further, the candidate server information storage unit 232 stores the host name of the user terminal device that is permitted to perform mail transmission under such a network environment, the source mail address of the email that is permitted to be transmitted, and the like.

  FIG. 6 shows an example of the candidate server information storage unit 232. As shown in FIG. 6, the candidate server information storage unit 232 includes “DNS host name”, “DNS IP address”, “SMTP host name”, “SMTP IP address”, “host name”, “sender address”, “ It has an item such as “expiration date”. Each item corresponds to each item included in the valid server information storage unit 231 illustrated in FIG.

  For example, the first line of the candidate server information storage unit 232 shown in FIG. 6 indicates that mail transmission may be permitted in a network environment that accesses a DNS server whose host name is “dns.xxx.co.jp”. Indicates a condition. Specifically, the first line of the candidate server information storage unit 232 shown in FIG. 6 indicates that there is a possibility that the use of the SMTP server whose host name is “smtp.xxx.co.jp” may be permitted. Show. In addition, the first line of the candidate server information storage unit 232 illustrated in FIG. 6 indicates that there is a possibility that mail transmission by a user terminal device whose host name is “* .xxx.co.jp” may be permitted. . For example, in the first line of the candidate server information storage unit 232 shown in FIG. 6, the mail transmission by the user terminal device having the host name “AAA.xxx.co.jp” or “BBB.xxx.co.jp” is performed. Indicates that it may be allowed. In addition, the first line of the candidate server information storage unit 232 shown in FIG. 6 may allow an e-mail with a source mail address “foo@xxx.co.jp” to be sent to the SMTP server. Indicates that there is sex. The first line of the candidate server information storage unit 232 illustrated in FIG. 6 indicates that various conditions are valid until “February 10, 2010”. The first line of the candidate server information storage unit 232 illustrated in FIG. 6 indicates that the DNS server IP address and the SMTP server IP address may be any value.

  The invalid server information storage unit 233 stores a combination of name server specifying information for specifying a DNS server and mail server specifying information for specifying an SMTP server that is not used in a network environment for accessing the DNS server. The invalid server information storage unit 233 stores a host name of a user terminal device that is not permitted to send mail under such a network environment, a source mail address of an email that is not allowed to be sent, and the like. In other words, the invalid server information storage unit 233 stores, as a black list, conditions in which the user terminal device 200 is not permitted to send an e-mail.

  FIG. 7 shows an example of the invalid server information storage unit 233. As shown in FIG. 7, the invalid server information storage unit 233 includes “DNS host name”, “DNS IP address”, “SMTP host name”, “SMTP IP address”, “host name”, “sender address”, “ It has an item such as “expiration date”. Each item corresponds to each item included in the valid server information storage unit 231 illustrated in FIG.

  In the second embodiment, the various conditions stored in the invalid server information storage unit 233 are used when the conditions stored in the valid server information storage unit 231 and the candidate server information storage unit 232 are not satisfied. To do. For example, when the invalid server information storage unit 233 illustrated in FIG. 7 does not satisfy the various conditions stored in the valid server information storage unit 231 and the candidate server information storage unit 232, the host name is “smtp.xxx. co.jp "indicates that use of the SMTP server is not permitted.

  The log storage unit 234 stores various types of information related to mail transmission processing. For example, the log storage unit 234 stores a mail transmission date and time, a transmission source mail address, a host name and IP address of the user terminal device 200 that is a transmission source, and a host name and IP address of a destination SMTP server. Further, the log storage unit 234 stores, for example, the host name and IP address of the DNS server that is an access target in the network environment at the time of mail transmission, the transmission result, the determination result by the determination unit 272 described later, and the like.

  The mail transmission / reception unit 260 includes a mail monitoring unit 270 and a network monitoring unit 280. The network monitoring unit 280 monitors the state of the network to which the user terminal device 200 belongs. Specifically, the network monitoring unit 280 accesses the DNS server and acquires the host name of the DNS server. Further, the network monitoring unit 280 acquires the IP address of the SMTP server by transmitting the host name of the communication destination SMTP server to the DNS server.

  As described above, the user terminal device 200 holds the IP address of the DNS server to be accessed, and changes the DNS server to be accessed according to the network environment to which the own device belongs. That is, the network monitoring unit 280 obtains the host name of the DNS server and the IP address of the destination SMTP server by accessing the DNS server corresponding to the network environment to which the device itself belongs.

  The mail monitoring unit 270 includes a monitoring unit 271, a determination unit 272, an inquiry unit 273, a storage unit 274, and a connection unit 275. The monitoring unit 271 monitors whether or not mail transmission is performed by the mail transmission / reception unit 260. When the monitoring unit 271 detects that mail transmission is performed by the mail transmission / reception unit 260, the monitoring unit 271 acquires the host name of the DNS server and the IP address of the SMTP server from the network monitoring unit 280. Instruct.

  For example, the monitoring unit 271 detects that mail transmission is performed by the mail transmission / reception unit 260 when a mail transmission operation is performed by the user using the input unit 210. In addition, when it is set to perform mail transmission at a predetermined time, the monitoring unit 271 detects that the mail transmission / reception unit 260 performs mail transmission when the predetermined time is reached.

  The determination unit 272 determines whether or not to permit mail transmission by the mail transmission / reception unit 260 based on various types of information acquired by the network monitoring unit 280 and various types of information stored in the storage unit 230. Specifically, as shown in FIG. 4, the determination unit 272 includes a first determination unit 272a, a second determination unit 272b, and a third determination unit 272c.

  The first determination unit 272a stores the effective server information in which the combination of the DNS server host name and IP address, the SMTP server host name and IP address, the host name of the local device, and the source mail address of the outgoing mail is stored. Whether it is stored in the unit 231 or not is determined. Hereinafter, the combination of the six pieces of information described above may be referred to as “server combination information”.

  In the second embodiment, it is assumed that the user terminal device 200 holds the DNS server IP address, the SMTP server host name, and the host name of its own device in the server combination information in advance. Of the server combination information, the host name of the DNS server and the IP address of the SMTP server are acquired by the network monitoring unit 280. In the server combination information, the transmission source mail address of the transmission mail is information set in the transmission mail and is input by the user.

  That is, the first determination unit 272a uses the information held in advance by the user terminal device 200, the information acquired by the network monitoring unit 280, and the information set in the email to be transmitted, to determine the determination process. I do. Then, when the server combination information is stored in the valid server information storage unit 231, the first determination unit 272a notifies the connection unit 275 that mail transmission is permitted. On the other hand, when the server combination information is not stored in the valid server information storage unit 231, the first determination unit 272a instructs the second determination unit 272b to perform a determination process.

  When the first determination unit 272a determines that the server combination information is not stored in the valid server information storage unit 231, the second determination unit 272b stores the server combination information in the candidate server information storage unit 232. It is determined whether or not. When the server combination information is stored in the candidate server information storage unit 232, the second determination unit 272b makes an inquiry to the inquiry unit 273 as to whether or not to send a mail. Instruct. On the other hand, when the server combination information is not stored in the candidate server information storage unit 232, the second determination unit 272b instructs the third determination unit 272c to perform the determination process.

  When the second determination unit 272b determines that the server combination information is not stored in the candidate server information storage unit 232, the third determination unit 272c stores the server combination information in the invalid server information storage unit 233. It is determined whether or not. Then, the third determination unit 272c notifies the inquiry unit 273 of the determination result.

  Note that the first determination unit 272a, the second determination unit 272b, and the third determination unit 272c have the current date and time stored in the expiration date among the various information stored in the effective server information storage unit 231 and the like. The determination process is performed by excluding records that are past the date and time.

  The inquiry unit 273 inquires of the user whether or not to send and receive electronic mail. Specifically, when the second determination unit 272b determines that the server combination information is stored in the candidate server information storage unit 232, the inquiry unit 273 asks the user whether to send an email. The display unit 220 controls display on the output unit 220. The inquiry unit 273 also displays a screen for inquiring the user whether or not to perform mail transmission even when the third determination unit 272c determines that the server combination information is not stored in the invalid server information storage unit 233. Is controlled to be displayed on the output unit 220. In addition, when the third determination unit 272c determines that the server combination information is stored in the invalid server information storage unit 233, the inquiry unit 273 displays a screen indicating that mail transmission is not permitted. Output to.

  In the following, a screen for inquiring the user whether or not to perform mail transmission may be referred to as an “inquiry screen”. Hereinafter, a screen indicating that mail transmission is not permitted may be referred to as a “warning screen”.

  8 and 9 show an example of an inquiry screen whose display is controlled by the inquiry unit 273. FIG. As shown in the upper part of FIG. 8, the inquiry unit 273 controls the output unit 220 to display an inquiry screen 10 </ b> G that displays that mail transmission has been blocked. The inquiry screen 10G has a cancel button 11B and a transmission confirmation button 12B.

  Here, when the user presses the cancel button 11B of the inquiry screen 10G using the input unit 210, the mail transmission / reception unit 260 does not transmit an email. On the other hand, when the transmission confirmation button 12B on the inquiry screen 10G is pressed by the user, the inquiry unit 273 controls the output unit 220 to display the inquiry screen 20G illustrated in the lower part of FIG.

  As shown in the lower part of FIG. 8, the inquiry screen 20 </ b> G has a tab or button for the user to select either “registration transmission” or “temporary transmission”. In FIG. 8, the inquiry screen 20G shows an example in which “registration transmission” is selected. The inquiry screen 20G illustrated in the lower part of FIG. 8 includes a pull-down for allowing the user to select information to be registered in the valid server information storage unit 231, a cancel button 21B, and a registration transmission button 22B. When the host name of the user terminal device 200 is “yyy.vpn.xxx.co.jp”, “yyy.vpn.xxx.co.jp”, “yyy.vpn.xxx.co.jp”, “ * .vpn.xxx.co.jp "and" * .xxx.co.jp ".

  Here, when the cancel button 21B of the inquiry screen 20G is pressed by the user, the mail transmission / reception unit 260 does not transmit an email. On the other hand, when the registration transmission button 22B on the inquiry screen 20G is pressed by the user, the inquiry unit 273 notifies the storage unit 274 of the information selected by the “host registration” pull-down and transmits the mail. The determination unit 272 is notified of permission.

  FIG. 9 shows an example of an inquiry screen 30G in which “temporary transmission” is selected after transmission confirmation is pressed on the inquiry screen 10G. As shown in the lower part of FIG. 9, the inquiry screen 30G includes a cancel button 31B, a temporary transmission button 32B, and an automatic learning function check box 33B. The automatic learning function check box 33B allows the user to select whether or not to register such a condition in the valid server information storage unit 231 when an e-mail is temporarily transmitted by pressing the temporary transmission button 32B. This is a check box.

  Here, when the temporary transmission button 32B is pressed by the user, the inquiry unit 273 notifies the determination unit 272 that mail transmission is permitted. At this time, when the automatic learning function check box 33B is selected, the inquiry unit 273 stores information indicating that the automatic learning function is selected, server combination information, and the like in the log storage unit 234.

  Next, FIG. 10 shows an example of a warning screen 40G whose display is controlled by the inquiry unit 273. As shown in FIG. 10, when the third determination unit 272c determines that the server combination information is stored in the invalid server information storage unit 233, the inquiry unit 273 displays that mail transmission is not permitted. Control.

  Returning to the description of FIG. 4, the storage unit 274 stores various types of information in the valid server information storage unit 231 based on the information received from the inquiry unit 273 and the information stored in the log storage unit 234. Specifically, when the storage unit 274 receives from the inquiry unit 273 the host information selected by the “host registration” pull-down on the inquiry screen 20G illustrated in FIG. The server combination information is stored in the valid server information storage unit 231. In addition, the storage unit 274 analyzes the log stored in the log storage unit 234 by the inquiry unit 273, so that when the server combination information temporarily transmitted by selecting the automatic learning function exists more than a predetermined number of times, Such server combination information is stored in the effective server information storage unit 231.

  By storing the server combination information in the valid server information storage unit 231 by the storage unit 274 in this way, the mail transmission / reception unit 260 makes an inquiry to the user when the conditions are the same as the stored server combination information. Email can be sent automatically without any problem. Further, the user can maintain various information stored in the valid server information storage unit 231 when performing mail transmission.

  The connection unit 275 establishes a communication connection with the SMTP server when mail transmission is permitted by the determination unit 272. Specifically, when the first determination unit 272a determines that the server combination information is stored in the valid server information storage unit 231, the connection unit 275 establishes a communication connection with the SMTP server. The connection unit 275 establishes a communication connection with the SMTP server when mail transmission is permitted by the determination unit 272 as a result of the inquiry by the inquiry unit 273.

  In addition, the connection unit 275 causes the determination unit 272 to perform the determination process again after the communication connection establishment process ends. The reason why the determination process by the determination unit 272 is performed again will be described using the example shown in FIG. In the example illustrated in FIG. 2, it is assumed that the user terminal device 200 a is connected to the intranet through the VPN and receives an operation of transmitting an e-mail to the SMTP server 21. Then, it is assumed that the determination unit 272 of the user terminal device 200a permits mail transmission by the first determination process. In such a case, the connection unit 275 of the user terminal device 200a performs processing for establishing a communication connection with the SMTP server 21.

  Here, there is a possibility that the VPN line is disconnected after the determination processing by the determination unit 272 ends and before the communication connection establishment processing by the connection unit 275 ends. If the VPN line is disconnected after the determination process by the determination unit 272 is completed, and then the connection unit 275 starts the communication connection establishment process, the connection unit 275 establishes information indicating that the communication connection is established in the Internet environment. Send. If there is a malicious server in the Internet environment, the connection unit 275 of the user terminal device 200a may establish a communication connection with the malicious server and send an electronic mail including an ID, a password, and the like to the server. is there.

  Therefore, the connection unit 275 causes the determination unit 272 to perform the determination process again after the communication connection establishment process is completed, so that the connection with the SMTP server that matches the conditions stored in the valid server information storage unit 231 is established. It can be determined that a communication connection has been established. In the above example, if the connection unit 275 establishes a communication connection with the SMTP server 21 after the determination processing by the determination unit 272 is completed, and then the VPN line is disconnected, an error occurs in mail transmission. Therefore, the problem of information leakage does not occur. This is because when the VPN line is disconnected after the communication connection is established, the communication connection is also disconnected.

  Next, processing by the user terminal device 200 according to the second embodiment will be described using the example illustrated in FIG. Here, the host name of the DNS server 11 is “dns.vpn.xxx.co.jp”, and the IP address of the DNS server 11 is “10.xxx.193.2”. In addition, the host name of the SMTP server 21 is “smtp.xxx.co.jp”, and the IP address of the SMTP server 21 is “10.xxx.192.3”. Further, the host name of the DNS server 12 is “dns.xxx.ne.jp”, and the IP address of the DNS server 12 is “10.xxx.100.2”. The host name of the SMTP server 22 is “smtp.xxx.ne.jp”, and the IP address of the SMTP server 22 is “10.xxx.100.3”.

  Here, it is assumed that the user terminal device 200a illustrated in FIG. 2 receives an operation for transmitting an e-mail from the user to the SMTP server 21. It is assumed that the host name of the user terminal device 200a is “aaa.vpn.xxx.co.jp” and the source mail address is “foo@xxx.co.jp”. In such a case, the user terminal device 200 a obtains the host name “dns.vpn.xxx.co.jp” of the DNS server 11 from the DNS server 11. In addition, the user terminal device 200 a acquires the IP address “10.xxx.193.2” of the SMTP server 21 from the DNS server 11. In the user terminal device 200a, the combination of the host name and IP address of the DNS server 11, the host name and IP address of the SMTP server 21, the host name of the own device, and the source mail address is an effective server information storage unit. It is determined whether it is stored in H.231 or the like. Here, since the server combination information is stored in the valid server information storage unit 231, the user terminal device 200 a transmits an e-mail.

  In addition, it is assumed that the user terminal device 200a illustrated in FIG. 2 receives an operation for transmitting an e-mail from the user to the SMTP server 22. It is assumed that the host name of the user terminal device 200a is “aaa.vpn.xxx.co.jp” and the source mail address is “foo@xxx.co.jp”. In such a case, the user terminal device 200 a obtains the host name “dns.vpn.xxx.co.jp” of the DNS server 11 from the DNS server 11. Further, the user terminal device 200 a acquires the IP address of the SMTP server 22 from the DNS server 11. Here, it is assumed that the DNS server 11 does not hold the IP address of the SMTP server 22. That is, the user terminal device 200a cannot acquire the IP address of the SMTP server 22 from the DNS server 11. In such a case, the user terminal device 200 a determines that the server combination information is not stored in the valid server information storage unit 231 and the candidate server information storage unit 232. And since the server combination information is not memorize | stored in the invalid server information memory | storage part 233, the user terminal device 200a controls display of the inquiry screen illustrated in FIG.8 and FIG.9 on the output part 220. FIG.

  Further, it is assumed that the user terminal apparatus 200b connected to the Internet shown in FIG. 2 accepts an operation for transmitting an e-mail from the user to the SMTP server 21. It is assumed that the host name of the user terminal device 200b is “bbb.xxx.ne.jp” and the source mail address is “foo@xxx.ne.jp”. In this case, the user terminal device 200b obtains the host name “dns.xxx.ne.jp” of the DNS server 12 from the DNS server 12. Further, the user terminal device 200 b acquires the IP address of the SMTP server 21 from the DNS server 12. Here, it is assumed that the DNS server 12 does not hold the IP address of the SMTP server 21. That is, the user terminal device 200b cannot acquire the IP address of the SMTP server 21 from the DNS server 12. In such a case, the user terminal device 200 b determines that the server combination information is not stored in the valid server information storage unit 231 and the candidate server information storage unit 232. And since the server combination information is memorize | stored in the invalid server information storage part 233, the user terminal device 200b carries out display control of the warning screen illustrated in FIG.

[Mail Transmission / Reception Processing Procedure by User Terminal Device According to Second Embodiment]
Next, a procedure of mail transmission / reception processing by the user terminal device 200 according to the second embodiment will be described with reference to FIG. FIG. 11 is a flowchart illustrating a mail transmission / reception processing procedure performed by the user terminal device 200 according to the second embodiment.

  As shown in FIG. 11, the monitoring unit 271 of the mail monitoring unit 270 monitors whether the mail transmission process is started (step S101). Then, when it is detected by the monitoring unit 271 that the mail transmission process is started (Yes at Step S101), the network monitoring unit 280 acquires the host name of the DNS server from the DNS server (Step S102). Further, the network monitoring unit 280 acquires the IP address of the SMTP server by transmitting the host name of the SMTP server used by the user terminal device 200 to the DNS server (step S103).

  Subsequently, the determination unit 272 performs determination processing for determining whether or not to permit mail transmission based on various information acquired by the network monitoring unit 280 and various information stored in the storage unit 230. (Step S104). Note that the determination processing procedure by the determination unit 272 will be described later with reference to FIG.

  When the determination unit 272 does not permit the email transmission (No at Step S105), the email transmission / reception unit 260 ends the email transmission process. On the other hand, when the determination unit 272 permits the mail transmission (Yes at Step S105), the connection unit 275 establishes a communication connection with the SMTP server (Step S106).

  Subsequently, the determination unit 272 performs the determination process again after the communication connection establishment process by the connection unit 275 is completed (step S107). The determination process in step S107 is the same as the determination process in step S104.

  Subsequently, when the determination unit 272 does not permit the mail transmission (No at Step S108), the connection unit 275 disconnects the communication connection with the SMTP server (Step S109) and ends the process. .

  On the other hand, when the mail transmission is permitted by the determination unit 272 (Yes at Step S108), the mail transmission / reception unit 260 transmits an electronic mail to the SMTP server (Step S110).

[Judgment procedure by judgment unit]
Next, the procedure of the determination process shown in steps S104 and S107 of FIG. 11 will be described using FIG. FIG. 12 is a flowchart illustrating a determination processing procedure by the determination unit 272.

  As shown in FIG. 12, first, the first determination unit 272a of the determination unit 272 determines whether or not the server combination information is stored in the valid server information storage unit 231 (step S201). Then, when the server combination information is stored in the valid server information storage unit 231 (Yes at Step S201), the determination unit 272 permits transmission of an e-mail (Step S202).

  On the other hand, when the first determination unit 272a determines that the server combination information is not stored in the valid server information storage unit 231 (No in step S201), the second determination unit 272b of the determination unit 272 performs the determination process. . Specifically, the second determination unit 272b determines whether or not the server combination information is stored in the candidate server information storage unit 232 (step S203).

  When the second determination unit 272b determines that the server combination information is stored in the candidate server information storage unit 232 (Yes in step S203), the inquiry unit 273 displays an inquiry screen on the output unit 220. Control (step S204).

  In such an inquiry screen, when an operation to send an e-mail is performed by the user (Yes at step S205), the storage unit 274 displays the information received from the inquiry unit 273 and the server combination information as valid server information. The data is stored in the storage unit 231 (step S206). Then, the determination unit 272 permits sending an e-mail (step S207). On the other hand, if the user performs an operation not to send an email on the inquiry screen (No at step S205), the determination unit 272 ends the process without allowing the email to be sent. .

  If the second determination unit 272b determines that the server combination information is not stored in the candidate server information storage unit 232 (No at Step S203), the third determination unit 272c of the determination unit 272 performs the determination process. . Specifically, the third determination unit 272c determines whether or not the server combination information is stored in the invalid server information storage unit 233 (step S208).

  When the third determination unit 272c determines that the server combination information is not stored in the invalid server information storage unit 233 (No at Step S208), the inquiry unit 273 displays an inquiry screen on the output unit 220. Control is performed (step S209). In the inquiry screen, when an operation for performing mail transmission is performed by the user (Yes at Step S210), the determination unit 272 permits transmission of an electronic mail (Step S211). On the other hand, when the user performs an operation not to send an e-mail on the inquiry screen (No at Step S210), the determination unit 272 ends the process without allowing the e-mail to be sent. .

  In addition, when the third determination unit 272c determines that the server combination information is stored in the invalid server information storage unit 233 (Yes in step S208), the inquiry unit 273 displays a warning screen on the output unit 220. Control is performed (step S212). And the determination part 272 complete | finishes a process, without permitting transmission of an email.

[Effect of Example 2]
As described above, the user terminal device 200 according to the second embodiment corresponds to the effective server information storage unit 231 with information about a DNS server, information about a mail server used in a network environment that accesses the DNS server, and the like. Hold on. Then, the user terminal device 200 determines whether or not server combination information such as information related to the DNS server to be accessed and information related to the SMTP server as the communication destination is stored in the valid server information storage unit 231 at the time of mail transmission. Thereby, the user terminal device 200 according to the second embodiment can determine the validity of the SMTP server of the communication destination. For example, the user terminal device 200 is controlled so as not to transmit information to be transmitted to the intranet to the Internet environment even when the user terminal device 200 is connected to the Internet environment and receives a mail transmission / reception operation in the intranet environment. it can. As a result, the user terminal device 200 according to the second embodiment can prevent leakage of information transmitted and received during mail transmission / reception.

  Further, in the case where the server combination information is not stored in the valid server information storage unit 231, the user terminal device 200 according to the second embodiment determines whether or not such server combination information is stored in the candidate server information storage unit 232. Determine. When the server combination information is stored in the candidate server information storage unit 232, the user terminal device 200 inquires of the user whether or not to send an e-mail. Thereby, even if the user terminal device 200 according to the second embodiment does not match the conditions stored in the valid server information storage unit 231, the user terminal device 200 can transmit an e-mail according to the judgment of the user. .

  Further, in the user terminal device 200 according to the second embodiment, the server combination information is stored in the candidate server information storage unit 232, and the server combination information is stored in the effective server information storage unit 231 when an e-mail is transmitted. To do. Thereby, the user terminal device 200 according to the second embodiment can maintain various types of information stored in the valid server information storage unit 231. As a result, the user terminal device 200 can reduce time and labor for the user to maintain the effective server information storage unit 231.

  Further, the user terminal device 200 according to the second embodiment determines whether or not the server combination information is stored in the invalid server information storage unit 233 when the server combination information is not stored in the candidate server information storage unit 232. judge. Then, when the server combination information is not stored in the invalid server information storage unit 233, the user terminal device 200 inquires whether or not to send an e-mail to the user. Further, when the server combination information is stored in the invalid server information storage unit 233, the user terminal device 200 does not transmit an e-mail. That is, since the user terminal device 200 does not transmit an e-mail when a condition that does not permit transmission of the e-mail is met, it is possible to prevent erroneous transmission of the e-mail due to a user's operation error.

  Also, the user terminal device 200 according to the second embodiment determines whether or not to send an e-mail again after performing a process of establishing a communication connection with the SMTP server. As a result, the user terminal device 200 according to the second embodiment performs a process of establishing a communication connection with the SMTP server, and then the user terminal device 200 is connected to the SMTP server even when the line connected to the SMTP server is disconnected. It can be determined whether or not a communication connection has been established. As a result, the user terminal device 200 can prevent sending an e-mail to an unintended SMTP server.

  In addition, the user terminal device 200 according to the second embodiment determines whether or not the server combination information including the mail address of the transmission source is stored in the valid server information storage unit 231 or the like. As a result, the user terminal device 200 according to the second embodiment can prevent an e-mail in which the e-mail address is set from being transmitted even when the user erroneously inputs the e-mail address. it can. For example, some users may use a mail address provided by a company and a mail address provided by a personally contracted provider. In such a case, the user must enter a company email address when sending email from the intranet environment, and enter a personal email address when sending email from the Internet environment. become. At this time, the user may input his / her mail address by mistake. The user terminal device 200 according to the second embodiment can prevent an e-mail in which the e-mail address is set from being transmitted when the e-mail address is erroneously input by the user.

  Note that the mail monitoring unit 270 and the network monitoring unit 280 illustrated in FIG. This will be described with reference to FIG. FIG. 13 is a block diagram illustrating a configuration example of a user terminal device according to the second embodiment. The user terminal device 300 illustrated in FIG. 13 is different from the user terminal device 200 illustrated in FIG. 3 in that it includes a mail transmission / reception unit 360, a mail monitoring unit 370, and a network monitoring unit 380. The mail transmitting / receiving unit 360 corresponds to the mail transmitting / receiving unit 260 illustrated in FIG. 3, but does not hold the mail monitoring unit 270 and the network monitoring unit 280. The mail monitoring unit 370 corresponds to the mail monitoring unit 270 illustrated in FIG. 3, and the network monitoring unit 380 corresponds to the network monitoring unit 280 illustrated in FIG.

  In the example illustrated in FIG. 13, the mail transmission / reception unit 360 transmits mail to the SMTP server via the mail monitoring unit 370 and the network monitoring unit 380. For example, the mail monitoring unit 370 and the network monitoring unit 380 are incorporated in an OS (Operating System), and catch an electronic mail transmitted from the mail transmission / reception unit 360 by the function of the OS. For example, the mail monitoring unit 370 and the network monitoring unit 380 may be incorporated in the communication control unit 240, the IF unit 250, and the like.

  By the way, the mail transmitting / receiving apparatus disclosed in the present application may be implemented in various different forms other than the above-described embodiments. Therefore, in the third embodiment, another embodiment such as a mail transmitting / receiving apparatus disclosed in the present application will be described.

[Receive processing]
In the second embodiment, the case where an e-mail is transmitted has been described as an example. However, the user terminal device 200 may perform the above-described determination process even when an e-mail is received. Specifically, the user terminal device 200 acquires name server specifying information by accessing a DNS server when performing e-mail reception processing. Then, the user terminal device 200 determines whether or not a combination of the acquired name server specifying information and mail server specifying information of a POP (Post Office Protocol) server as a communication destination is stored in the effective server information storage unit 231 or the like. judge. Then, when the POP server is valid, the user terminal device 200 transmits an ID and a password to the POP server and acquires an e-mail.

[Items to be judged]
In the second embodiment, the combination of the DNS server host name and IP address, the SMTP server host name and IP address, the user terminal device 200 host name, and the source mail address is stored in the valid server information storage unit 231 and the like. The example which determines whether it is memorize | stored was demonstrated. However, the user terminal device 200 according to the second embodiment can use any combination of information without determining whether all the information included in the server combination information is stored in the valid server information storage unit 231 or the like. It may be determined whether it is stored in the server information storage unit 231 or the like. For example, the user terminal device 200 determines whether the combination of the DNS server host name and the SMTP server IP address among the information included in the server combination information is stored in the valid server information storage unit 231 or the like. May be.

  Further, the user terminal device 200 may receive an operation for setting a security level from the user, and may select information for determining whether or not the information is stored in the valid server information storage unit 231 according to the security level. For example, when the highest security level is set, the user terminal device 200 may determine whether all the information included in the server combination information is stored in the valid server information storage unit 231 or the like. . Further, for example, when the user terminal device 200 is set to the lowest security level, is the combination of the DNS server host name and the SMTP server IP address stored in the valid server information storage unit 231 or the like? It may be determined whether or not.

[Server combination information items]
Further, the server combination information described in the second embodiment may include a destination mail address set in an electronic mail, a subject (Subject), and the like. Further, the valid server information storage unit 231 and the like may store conditions such as a destination mail address and a subject. Then, the user terminal device 200 may determine whether or not the server combination information including the destination mail address and the subject name is stored in the valid server information storage unit 231 or the like.

[Judgment process order]
Moreover, in the said Example 2, after the 1st determination part 272a performed the determination process, the 2nd determination part 272b performed the determination process, and the 3rd determination part 272c performed the determination process after that. However, the user terminal device 200 may not perform the determination process in the above order. For example, the user terminal device 200 may perform the determination process by the first determination unit 272a after performing the determination process by the third determination unit 272c. In such a case, various types of information stored in the valid server information storage unit 231 and the invalid server information storage unit 233 are different from the examples illustrated in FIGS.

  Further, the user terminal device 200 may not perform all the determination processes. For example, the user terminal device 200 may perform only the determination process by the first determination unit 272a and the determination process by the third determination unit 272c. The order of the determination processes and the selection of the determination processes may be set by the user.

[program]
The various processes described in the above embodiments can be realized by executing a prepared program on a computer. In the following, an example of a computer that executes a mail transmission / reception program having the same function as that of the mail transmission / reception apparatus 100 illustrated in FIG. 1 will be described with reference to FIG.

  FIG. 14 is a diagram illustrating a computer that executes a mail transmission / reception program. As illustrated in FIG. 14, the computer 1000 includes a RAM 1010, a cache 1020, an HDD 1030, a ROM 1040, a CPU 1050, and a bus 1060. The RAM 1010, cache 1020, HDD 1030, ROM 1040, and CPU 1050 are connected by a bus 1060.

  The ROM 1040 stores in advance a mail transmission / reception program that exhibits the same functions as the mail transmission / reception apparatus 100 shown in FIG. Specifically, the ROM 1040 stores an acquisition program 1041, a determination program 1042, and a connection program 1043.

  Then, the CPU 1050 reads and executes the acquisition program 1041, the determination program 1042, and the connection program 1043. Accordingly, as illustrated in FIG. 14, the acquisition program 1041 becomes the acquisition process 1051, the determination program 1042 becomes the determination process 1052, and the connection program 1043 becomes the connection process 1053. The acquisition process 1051 corresponds to the acquisition unit 120 illustrated in FIG. 1, the determination process 1052 corresponds to the determination unit 130 illustrated in FIG. 1, and the connection process 1053 corresponds to the connection unit 140 illustrated in FIG. Correspond.

  Further, the HDD 1030 is provided with a server information storage unit 1031 as shown in FIG. The server information storage unit 1031 corresponds to the valid server information storage unit 110 illustrated in FIG.

  Note that the programs 1041 to 1043 described above are not necessarily stored in the ROM 1040. For example, the programs 1041 to 1043 may be stored in a “portable physical medium” such as a flexible disk (FD), a CD-ROM, an MO disk, a DVD disk, a magneto-optical disk, or an IC card inserted into the computer 1000. . Alternatively, the programs 1041 to 1043 may be stored in a “fixed physical medium” such as a hard disk drive (HDD) provided inside or outside the computer 1000. Alternatively, the programs 1041 to 1043 may be stored in “another computer (or server)” connected to the computer 1000 via a public line, the Internet, a LAN, a WAN, or the like. Then, the computer 1000 may read and execute each program from the above-described flexible disk or the like.

[System configuration, etc.]
Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to that shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. For example, the inquiry unit 273 and the storage unit 274 illustrated in FIG. 4 may be integrated into the determination unit 272.

  The following supplementary notes are further disclosed with respect to the embodiments including the above examples.

(Additional remark 1) The effective server information storage part which memorize | stores the combination of the name server specific information which specifies a name server, and the mail server specific information which specifies the mail server used in the network environment which accesses the said name server,
An acquisition unit that acquires name server specifying information of the name server and mail server specifying information of a communication destination mail server from a name server to be accessed in a network to which the device belongs,
A first determination unit that determines whether a combination of the name server identification information and the mail server identification information acquired by the acquisition unit is stored in the valid server information storage unit;
When the first determination unit determines that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the first determination unit is not connected to the communication destination mail server. If the first determining unit determines that the combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit, the first determining unit connects to the communication destination mail server. A mail transmission / reception device comprising: a connection unit.

(Additional remark 2) The candidate server information storage part which memorize | stores the combination of the name server specific information which specifies a name server, and the mail server specific information which specifies the candidate of the mail server used in the network environment which accesses the said name server, ,
When the first determination unit determines that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the name server specifying information, the mail server specifying information, A second determination unit that determines whether or not the combination is stored in the candidate server information storage unit;
When it is determined by the second determination unit that a combination of the name server specifying information and the mail server specifying information is stored in the candidate server information storage unit, the name server specifying information and the mail server specifying The mail transmitting / receiving apparatus according to claim 1, further comprising a storage unit that stores a combination with information in the effective server information storage unit.

(Supplementary Note 3) When it is determined by the second determination unit that the combination of the name server specific information and the mail server specific information is stored in the candidate server information storage unit, an electronic message is sent to the user. It also has an inquiry section that inquires whether or not to send and receive emails.
When the storage unit receives information indicating that an e-mail is to be transmitted / received as a result of the inquiry by the inquiry unit, the storage unit stores the combination of the name server specifying information and the mail server specifying information in the effective server information storage. Store in the department,
3. The mail transmission / reception according to appendix 2, wherein the connection unit connects to the communication destination mail server when information indicating that the transmission / reception of an electronic mail is received as a result of the inquiry by the inquiry unit. apparatus.

(Additional remark 4) Invalid server information storage part which memorize | stores the combination of the name server specific information which specifies a name server, and the mail server specific information which specifies the mail server which is not used in the network environment which accesses the said name server,
A third determination unit that determines whether a combination of the name server identification information and the mail server identification information acquired by the acquisition unit is stored in the invalid server information storage unit;
When the third determination unit determines that the combination of the name server specifying information and the mail server specifying information is stored in the invalid server information storage unit, the connection unit sends the communication destination mail. The mail transmitting / receiving apparatus according to any one of appendices 1 to 3, wherein the mail transmitting / receiving apparatus is not connected to a server.

(Additional remark 5) The said acquisition part is the name server specific information of this name server from the name server which becomes an access object in the network to which an own apparatus belongs after the connection process with the said communication destination mail server is performed by the said connection part. And the mail server identification information of the destination mail server again,
The first determining unit determines whether the name server specifying information and the mail server specifying information acquired again by the acquiring unit are stored in the valid server information storage unit,
After the connection unit performs a connection process with the communication destination mail server, a combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit by the first determination unit. The mail transmitting / receiving apparatus according to appendix 1, wherein the mail transmitting / receiving apparatus disconnects the connection with the communication destination mail server when it is determined that the mail is not present.

(Additional remark 6) The said effective server information storage part further matches and memorize | stores a transmission origin mail address in the combination of name server specific information and mail server specific information,
The first determination unit stores, in the effective server information storage unit, a combination of the name server specifying information and mail server specifying information acquired by the acquiring unit and a transmission source mail address set in a transmission mail. To determine whether or not
In the connection unit, the combination of the name server identification information, the mail server identification information, and the transmission source mail address of the transmission mail is not stored in the valid server information storage unit by the first determination unit. If it is determined, the first determination unit does not connect to the communication destination mail server, and the combination of the name server specifying information, the mail server specifying information, and the source mail address of the transmission mail is The mail transmitting / receiving apparatus according to appendix 1, wherein the mail transmitting / receiving apparatus is connected to the communication destination mail server when it is determined that it is stored in the valid server information storage unit.

(Appendix 7) A mail transmission / reception method by a mail transmission / reception device for transmitting / receiving an electronic mail
The mail transmitting / receiving device is
An acquisition step of acquiring name server specifying information for specifying the name server and mail server specifying information for specifying a communication destination mail server from a name server to be accessed in a network to which the mail transmitting / receiving apparatus belongs;
The name server identification acquired by the acquisition step in the effective server information storage unit that stores the combination of the name server identification information of the name server and the mail server identification information of the mail server used in the network environment for accessing the name server A determination step of determining whether a combination of information and mail server identification information is stored;
When it is determined by the determination step that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the determination is made without connecting to the communication destination mail server. A step of connecting to the communication destination mail server if the step determines that the combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit. A mail transmission / reception method characterized by the above.

(Appendix 8) A mail transmission / reception program to be executed by a computer that transmits / receives electronic mail,
An acquisition procedure for acquiring name server specifying information for specifying the name server and mail server specifying information for specifying a communication destination mail server from a name server to be accessed in a network to which the device belongs,
The name server identification acquired by the acquisition procedure in the effective server information storage unit that stores the combination of the name server identification information of the name server and the mail server identification information of the mail server used in the network environment for accessing the name server A determination procedure for determining whether a combination of information and mail server specific information is stored;
When it is determined by the determination procedure that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the determination is made without connecting to the communication destination mail server. If it is determined by the procedure that the combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit, a connection procedure for connecting to the communication destination mail server is sent to the computer. A mail transmission / reception program characterized by being executed.

DESCRIPTION OF SYMBOLS 1 Network 10 Name server 11, 12 DNS server 20 Mail server 21, 22 SMTP server 100 Mail transmission / reception apparatus 110 Effective server information storage part 120 Acquisition part 130 Determination part 140 Connection part 200, 200a, 200b, 300 User terminal apparatus 210 Input part 220 output unit 230 storage unit 231 valid server information storage unit 232 candidate server information storage unit 233 invalid server information storage unit 234 log storage unit 240 communication control unit 250 IF unit 260, 360 mail transmission / reception unit 270, 370 mail monitoring unit 271 monitoring unit 272 determination unit 272a first determination unit 272b second determination unit 272c third determination unit 273 inquiry unit 274 storage unit 275 connection unit 280, 380 network monitoring unit

Claims (7)

An effective server information storage unit for storing a combination of name server specifying information for specifying a name server and mail server specifying information for specifying a mail server used in a network environment for accessing the name server;
An acquisition unit that acquires name server specifying information of the name server and mail server specifying information of a communication destination mail server from a name server to be accessed in a network to which the device belongs,
A first determination unit that determines whether a combination of the name server identification information and the mail server identification information acquired by the acquisition unit is stored in the valid server information storage unit;
When the first determination unit determines that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the first determination unit is not connected to the communication destination mail server. If the first determining unit determines that the combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit, the first determining unit connects to the communication destination mail server. A mail transmission / reception device comprising: a connection unit. A candidate server information storage unit for storing a combination of name server specifying information for specifying a name server, and mail server specifying information for specifying a mail server candidate used in a network environment for accessing the name server;
When the first determination unit determines that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the name server specifying information, the mail server specifying information, A second determination unit that determines whether or not the combination is stored in the candidate server information storage unit;
When it is determined by the second determination unit that a combination of the name server specifying information and the mail server specifying information is stored in the candidate server information storage unit, the name server specifying information and the mail server specifying The mail transmitting / receiving apparatus according to claim 1, further comprising a storage unit that stores a combination with information in the effective server information storage unit. When the second determination unit determines that the combination of the name server specifying information and the mail server specifying information is stored in the candidate server information storage unit, the user is sent and received an e-mail. A query section for inquiring whether or not
When the storage unit receives information indicating that an e-mail is to be transmitted / received as a result of the inquiry by the inquiry unit, the storage unit stores the combination of the name server specifying information and the mail server specifying information in the effective server information storage. Store in the department,
3. The mail according to claim 2, wherein the connection unit is connected to the communication destination mail server when information indicating that an email is transmitted and received is received as a result of the inquiry by the inquiry unit. Transmitter / receiver. An invalid server information storage unit for storing a combination of name server specifying information for specifying a name server and mail server specifying information for specifying a mail server that is not used in a network environment for accessing the name server;
A third determination unit that determines whether a combination of the name server identification information and the mail server identification information acquired by the acquisition unit is stored in the invalid server information storage unit;
When the third determination unit determines that the combination of the name server specifying information and the mail server specifying information is stored in the invalid server information storage unit, the connection unit sends the communication destination mail. The mail transmitting / receiving apparatus according to claim 1, wherein the mail transmitting / receiving apparatus is not connected to a server. After the connection unit is connected to the communication destination mail server by the connection unit, the acquisition unit receives name server identification information of the name server and communication destination mail from the name server to be accessed in the network to which the device belongs. Get the mail server specific information of the server again,
The first determining unit determines whether the name server specifying information and the mail server specifying information acquired again by the acquiring unit are stored in the valid server information storage unit,
After the connection unit performs a connection process with the communication destination mail server, a combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit by the first determination unit. The mail transmitting / receiving apparatus according to claim 1, wherein when it is determined that the mail is not present, the connection with the communication destination mail server is disconnected. A mail transmission / reception method by a mail transmission / reception device for transmitting / receiving an electronic mail,
The mail transmitting / receiving device is
An acquisition step of acquiring name server specifying information for specifying the name server and mail server specifying information for specifying a communication destination mail server from a name server to be accessed in a network to which the mail transmitting / receiving apparatus belongs;
The name server identification acquired by the acquisition step in the effective server information storage unit that stores the combination of the name server identification information of the name server and the mail server identification information of the mail server used in the network environment for accessing the name server A determination step of determining whether a combination of information and mail server identification information is stored;
When it is determined by the determination step that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the determination is made without connecting to the communication destination mail server. A step of connecting to the communication destination mail server if the step determines that the combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit. A mail transmission / reception method characterized by the above. A mail transmission / reception program to be executed by a computer that transmits / receives e-mail,
An acquisition procedure for acquiring name server specifying information for specifying the name server and mail server specifying information for specifying a communication destination mail server from a name server to be accessed in a network to which the device belongs,
The name server identification acquired by the acquisition procedure in the effective server information storage unit that stores the combination of the name server identification information of the name server and the mail server identification information of the mail server used in the network environment for accessing the name server A determination procedure for determining whether a combination of information and mail server specific information is stored;
When it is determined by the determination procedure that the combination of the name server specifying information and the mail server specifying information is not stored in the valid server information storage unit, the determination is made without connecting to the communication destination mail server. If it is determined by the procedure that the combination of the name server specifying information and the mail server specifying information is stored in the valid server information storage unit, a connection procedure for connecting to the communication destination mail server is sent to the computer. A mail transmission / reception program characterized by being executed.

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