JP2011159244A - E-mail transmission control program, operating method and computer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an E-mail transmission control program for preventing E-mails from being incorrectly transmitted, which can be easily introduced, without depending on network configuration or E-mail transmission software. <P>SOLUTION: The E-mail transmission control program is operated on the same computer device 1 as a mailer M as software for transmitting E-mails and includes: a network driver part N which intercepts the E-mails to be transmitted by the mailer M; a policy determination part P which determines whether the intercepted E-mail should be transmitted or not; and a proxy server function part S which determines whether the E-mail should be deleted or transmitted as it is to an E-mail server device 2, depending on the determination result by the policy determination part P. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an e-mail transmission control program for controlling transmission of an e-mail transmitted by an e-mail transmission / reception program and preventing erroneous transmission.

In recent years, the use of e-mail has become indispensable in business activities in all fields, and it has become normal to exchange over 100 e-mails a day.
While e-mail has the advantage of being easy and can be sent and received instantly, there are many cases where an e-mail is sent with wrong contents or the destination is wrong.

Therefore, a plurality of methods have been proposed to prevent such so-called erroneous transmission of electronic mail. There are several mechanisms to prevent erroneous transmission. (1) A type that adds a function for preventing erroneous email transmission to software for sending and receiving email installed on client devices handled by users. (2) Collecting and distributing emails. There is a type in which a function for preventing erroneous mail transmission is added on the mail server device side, and (3) a type in which a device for preventing erroneous transmission is separately provided for capturing an electronic mail erroneously transmitted between the client device and the mail server device. .
Among them, there is, for example, Patent Document 1 as the one (1).

JP 2007-193717 A

Each of the mechanisms (1) to (3) has certain problems and disadvantages.
First, when a function is added to the electronic mail transmission / reception software of the client device as in (1), an erroneous mail transmission prevention function is developed for at least all of the multiple electronic mail transmission / reception software that the user may use. There is a problem that it is necessary and development requires a large cost.
In addition, when the user uses e-mail transmission / reception software that does not have a function of preventing erroneous e-mail transmission, there is also a problem that e-mail transmission / reception cannot be prevented in the first place.

  In view of the problem of (1), a function for preventing erroneous mail transmission has been added to the device for preventing erroneous transmission placed on the mail server device side or between the mail server device and the client device as in (2) and (3). For example, if a company employee connects the client device to the in-house LAN and uses it, there will be no problem, but it is taken out on a business trip etc. and sent via another mail server. Therefore, it is impossible to prevent erroneous transmission.

  The present invention has been made in view of the above points, and prevents erroneous email transmission without depending on the type of email transmission / reception software, the configuration of a communication network when an email is transmitted, or the like. The purpose is to provide programs and the like that can be used.

  An e-mail transmission control program according to the present invention includes a network device unit and a proxy that are equipped with an e-mail transmission program for operating a computer device as an e-mail creating and transmitting unit that executes e-mail creation and transmission. The network driver unit is configured to operate as a server function unit and a policy determination unit. The network driver unit interrupts transmission of an IP data packet to be transmitted to the outside of the computer device, and the IP data packet is electronically transmitted. A determination means for determining whether or not it is mail; if the result of the determination is an electronic mail, the destination IP address of the IP data packet is set to the IP address of the computer device and the destination port number is set to the proxy server Used in the function section Sending means for setting and sending to the policy number, wherein the proxy server function part notifies the policy judgment part that the electronic mail has been received from the network driver part, and the policy judgment Determining means for deciding whether to discard or send the e-mail based on the determination information from the section, wherein the policy determination section is an acquisition means for acquiring policy data and an electronic device notified from the proxy server function section. A determination unit that determines whether or not the mail meets a condition defined in the policy data; and an information notification unit that notifies the proxy server function unit of determination information according to the determination result. (Claim 1).

Since the e-mail transmission control program of the present invention is mounted on the same computer apparatus as the e-mail transmission program for transmitting e-mail, the user takes out the client apparatus and transmits e-mail under a different network environment. Even when it is performed, it is possible to prevent erroneous mail transmission.
Further, this e-mail transmission control program is a different program from the e-mail transmission program and can target all e-mails to be sent from the computer device. It can be applied regardless of the type.

Furthermore, according to the present invention, the e-mail transmission control program can play a role of preventing erroneous mail transmission without affecting the operation of the e-mail transmission program. In other words, the e-mail creation and transmission unit (e-mail transmission program) only needs to execute the process of transmitting an e-mail to the e-mail server device regardless of the presence or absence of the e-mail transmission control program. There is no need to switch the operation according to the presence or absence.
Therefore, it is very advantageous in that it is not necessary to add special processing or change settings on the e-mail creation / transmission unit (e-mail transmission program) side. In addition, since it does not affect the operation of the e-mail creation / transmission unit (e-mail transmission program), even if the e-mail transmission control program is installed or uninstalled, the e-mail transmission program must be set each time. There is no need to change the setting.

  When the e-mail is delivered to the proxy server function unit, the network driver unit sets a response signal indicating that the e-mail has been received, and sets the return source IP address as the IP address of the e-mail server device. In addition, there may be further provided means for setting the reply source port number to the port number of the electronic mail server device and sending it to the electronic mail creating / transmitting section (claim 2).

Since the actual reply source of the response signal is the proxy server function unit in the same computer apparatus, the reply source IP address of the response signal is used for the IP address of the computer apparatus, and the reply source port number is used for the proxy server function part. Port number. However, since the e-mail creation / transmission unit (e-mail transmission program) is in a state of waiting for a response signal by transmitting an e-mail to the e-mail server apparatus, the reply source IP address of the response signal is the computer apparatus. If it is an IP address or the like, it cannot be recognized as a response signal to the e-mail transmitted by itself.
Therefore, the reply source IP address of the response signal is rewritten to the IP address of the electronic mail server device, and the reply source port number is set to the port number of the electronic mail server device, whereby the electronic mail creating and transmitting unit (email The transmission program) can recognize that the electronic mail server apparatus has returned. When viewed from the e-mail creation / transmission unit (e-mail transmission program), it can be determined that a response signal has been sent from the e-mail server device as a result of executing the e-mail transmission process to the e-mail server device. It can be recognized that the transmission process has been completed.
In this way, erroneous transmission of email without affecting the operation of the email creation and transmission unit (email transmission program) (without making the email transmission program aware of the presence of the email transmission control program of the present invention). The prevention process can be executed, which is convenient.

  The e-mail transmission control program is a program for operating the computer device as a discard notification function unit, and the discard notification function unit is discarded when the proxy server function unit discards the e-mail. Means for creating a discard notification e-mail in which the e-mail source mail address is set as the destination mail address, and means for sending the discard notification e-mail to the e-mail server device (Claim 3).

As a general rule, a user who operates an e-mail transmission program and sends an e-mail generally thinks that an e-mail has been sent when the process of the e-mail transmission program is completed normally. By separately notifying that the message has been discarded, the user can be made aware that the electronic mail to be transmitted is not permitted to be transmitted.
There are various ways to notify the user in this case, such as a method of displaying the information on the screen as a text message or a method of notifying the user with a voice. A method of sending a notification e-mail and notifying is more preferable.
Since the e-mail transmission program has a record of transmission of the e-mail to be transmitted, the fact that the e-mail has been discarded is also recorded in the e-mail transmission program so that the user can It is possible to recognize at once a series of facts that an attempt to send an e-mail was made by simply checking the record of the e-mail sending program, but it was discarded.

In this case, the discard notification e-mail may further include a reason why the e-mail is discarded (claim 4).
Normally, when an email that is attempted to be sent is discarded, it is considered that the user will re-edit the email after recognizing the reason, resolve the cause of the cancellation, and re-send the email. In order to support the re-editing, convenience can be further improved if the reason for the discarding can be presented to the user.

  In addition, the policy determination unit includes a display unit that displays to accept an input from a user, and the display unit includes a condition in which an e-mail notified from the proxy server function unit is defined in the policy data. The information may be displayed by the display unit when the information matches the above, and the information notification unit may include information corresponding to the input from the user received by the display unit in the determination information. Item 5).

  In addition to deciding whether to send an e-mail based on whether the policy decision part mechanically matches the policy, the policy decision unit also incorporates a mechanism that alerts the user and leaves the final decision to the user However, this is because flexibility is improved and convenience is improved.

  Note that the operation method of the computer device (Claim 6) and the computer device itself realized by using the electronic mail transmission control program are also very useful (Claim 7).

  As described above, according to the present invention, it is possible to easily realize a function for preventing erroneous transmission of electronic mail that does not depend on a network configuration or mail transmission software.

It is a schematic diagram which shows the outline | summary of the hardware constitutions of the computer apparatus concerning this invention. It is a schematic diagram which shows the relationship of the program mounted in the computer apparatus which concerns on this invention. It is a schematic diagram which shows the outline | summary of operation | movement sequences, such as each program of this invention. It is a schematic diagram which shows the communication procedure of SMTP. It is a figure which shows an example of the IP address and port number which are used in the electronic mail transmission control method by this invention. It is a figure which shows an example of the IP address and port number which are used in the electronic mail transmission control method by this invention.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing a hardware configuration of a computer apparatus 1 (client) that creates and transmits mail.

[Configuration overview]
The CPU 101 has a function of reading a computer program for realizing the functions of the computer device 1 from the hard disk 112, copying it to the memory 111, and executing it.
Examples of the computer program executed in the present invention include a program of an operating system (hereinafter referred to as OS) of the computer apparatus 1, an email transmission program M (hereinafter referred to as mailer), and an email transmission control program. .
In this case, the electronic mail transmission control program includes a network driver unit N, a proxy server function unit S, and a policy determination unit P.
The OS and the e-mail transmission control program are automatically read from the hard disk 112 and copied to the memory 111 when the computer apparatus 1 is turned on, and are always executable. In general, the user is read from the hard disk 112 and copied to the memory 111 at any time when the user creates or sends / receives mail.

Note that the OS includes a TCP / IP communication library for executing TCP / IP communication necessary for sending and receiving e-mails, and uses an API function prepared in advance to send and receive IP data packets. Can be done. This API function is used to exchange data between the TCP / IP communication library and the application program.
Then, with this TCP / IP communication library, an IP data packet to be transmitted from the computer apparatus 1 to the outside is transmitted to another computer apparatus (for example, the electronic mail server 2) via the communication interface 121, or from another computer apparatus. A function of receiving the IP data packet via the communication interface 121 is realized.

  Although FIG. 1 shows an example in which the computer device 1 has only one CPU, it may be constituted by a plurality of CPUs, and some of the functions to be realized are executed. A hardware configuration including a possible dedicated chip (IC or the like) may be used.

[Program operation]
Next, the operation of the e-mail transmission control program according to the present invention will be described in detail with reference to FIGS. FIG. 5 and FIG. 6 show the IP addresses, port numbers, and the like that are used.
Since the various programs appearing in the embodiment are combinations of instructions for the computer device 1, the main body of operations and functions realized by the program is the computer device 1, but in order to make it easier to understand the contents of the invention, In the following, various programs are described as the subject of operation.

[Mailer M settings]
The mailer M used by the user has a function of creating and transmitting / receiving an email, and the user can send an email created using the mailer M.
Normally, the mailer M is configured so that it does not operate unless the IP address and port number of the e-mail server to be used are set. Therefore, the IP address and port number of the e-mail server 2 are set in the mailer M. .
In the present invention, the IP address A2 and the port number N2 of the e-mail server 2 need only be set in the mailer M regardless of whether or not the e-mail transmission control program is installed in the computer device 1. It is not necessary to change this setting even if the mail transmission control program is installed.

Normally, when employees such as companies send and receive e-mail using computer devices connected to the in-house LAN, almost all employees use the same e-mail server prepared by the information system department of the company to send e-mails. In order to perform transmission / reception, it is often the case that all perform the same setting.
In the present invention, the IP address A2 and the port number N2 of the e-mail server 2 may be set regardless of whether or not the e-mail transmission control program is installed (before and after the e-mail transmission control program is installed / uninstalled). One of the merits is that the introduction is easy in that the setting does not have to be changed.

  If it is a mechanism that has to change the settings of the mailer M before and after the e-mail transmission control program is installed / uninstalled, there is inconvenience that it takes time to teach the setting method for each employee, In particular, when a different setting must be made for each computer device used by an employee, the time and effort required to teach the setting method are also increased. In addition, when there are many unfamiliar employees who forget to change settings or make mistakes, there is a problem that it becomes necessary to provide support for each individual employee. It hardly occurs.

[Outline of e-mail transmission processing using the basic SMTP procedure]
An API function prepared for using a TCP / IP communication library (hereinafter referred to as a communication library) T included in the OS of the computer apparatus 1 includes, for example, when mail transmission processing is executed by the mailer M. Sends an IP data packet to be sent to the port number as an argument, using a transmission function called as an argument for the destination or data content of the IP data packet to be sent, or an identifier such as a TCP socket generated in association with a specific port number There is a reception function that is called to receive the received IP data packet.
When the mailer M executes the transmission process of the e-mail, the e-mail transmission destination e-mail address, the pointer to the text data storing the character string of the e-mail body, the destination IP address, etc. are used as arguments. You can send an email by calling.

Note that when sending and receiving electronic mail, a protocol called SMTP (Simple Mail Transfer Protocol) is often used. In this SMTP, an exchange is performed between an electronic mail server and an electronic mail transmission / reception client device according to a predetermined communication procedure. This communication procedure will be described with reference to FIG.
The SMTP communication procedure is defined in the RFC (Request For Comment) of the IETF (Internet Engineering Task Force), and the following is the same as the procedure defined in the RFC.
First, a TCP communication connection is established between the electronic mail server and the client device. In this case, the port number of the electronic mail server is normally 25. The subsequent exchanges are performed by exchanging data in the IP data packet format over this TCP communication connection.

When the TCP communication connection is normally established, first, the client device transmits an EHLO command storing its own domain name. In response to this, the electronic mail server returns a response signal.
When the client apparatus receives a response signal to the EHLO command, the client apparatus transmits a MAIL command storing an e-mail source mail address (usually a user mail address) and an RCPT command storing a destination mail address.
When response signals can be received for these, a DATA command is transmitted to start transmission of the mail text. The data of the mail text can be divided into a plurality of IP data packets and transmitted according to the length of the mail. When all the data of the mail text has been sent, a code (period) indicating the end is transmitted, and then communication is completed with a QUIT command.
When the transmission of the e-mail is finished, the TCP communication connection is disconnected at that time.

[Overview of the operation of the e-mail transmission control program]
First, when the user operates the mailer M to create an e-mail and starts transmission processing (when a mailer M send button is pressed or the like), the mailer M establishes a TCP communication connection with the e-mail server 2. Try to establish.
When the TCP communication connection is established, the mailer M starts the e-mail transmission process according to the above-described SMTP procedure (Step 2 in FIG. 3).
Regarding the establishment of TCP communication connection and the e-mail transmission process by the mailer M, the network driver unit N performs the “preemption” described later after interrupting the process executed by the OS.

The network driver unit N has a function of hooking the transmission process of the IP data packet in the computer apparatus 1 (Step 1 in FIG. 3). This hook function interrupts the transmission process and delivers the IP data packet to the network driver unit when any application program requests the OS to transmit the IP data packet (calls the transmission function). That's it. With this hook function, the network driver unit N can “preempt” the IP data packet before the transmission process is actually executed (Step 3 in FIG. 3).
When the e-mail transmission process is executed by the mailer M, the transmission function of the OS communication library T is called, but this e-mail is also intercepted by the network driver unit N.
In order to enable the preemption by the hook function, a command for enabling the hook function is usually executed immediately after the computer apparatus 1 is started and immediately after the execution of the e-mail transmission control program is started. Then, every time the transmission function is called, the network driver unit N can “take over”.

If the intercepted IP data packet is irrelevant to the e-mail other than the e-mail data and command and its response signal, the network driver unit N performs some processing on the IP data packet. Without permission.
On the other hand, if the intercepted IP data packet relates to an electronic mail, the IP address A2 (“10.1.1.1” in FIG. 5) of the destination of the IP data packet is set to the IP address A1 of the computer device 1 itself. (“10.0.0. 1” in FIG. 5) and the destination port number N2 (“25” in FIG. 5) is used by a proxy server function unit (hereinafter referred to as a proxy) S described later. The port number is set to N1 (the port number used for receiving the IP data packet transmitted from the mailer M by the proxy S and transferred by the network driver unit N, “1021” in FIG. 5). Note that when the proxy S and the email server 2 use the same number, the port number may not be rewritten.
Then, the communication library T is instructed to transmit the IP data packet with the rewritten contents. Hereinafter, the process in which the communication library T transmits an e-mail after rewriting the destination IP address or the like is referred to as “transfer” (Step 4 in FIG. 3).

Whether the intercepted IP data packet is related to electronic mail is whether the destination or source port number of the IP data packet is a port number (usually 25) normally used in the SMTP protocol. It is good to judge by. However, in this case, if it is known that a port number other than 25 (for example, 2525) is used for the SMTP protocol, an IP data packet having a number other than 25 as a destination port number is electronically transmitted. It may be judged that it is related to mail. In addition, it is possible to determine that an IP data packet having one of a plurality of port numbers (for example, No. 25 and No. 2525) as a destination port number relates to an electronic mail.
Further, it may be determined whether or not it relates to an electronic mail from the format of the IP data packet other than the port number. Since the data format of the command exchanged according to the above-mentioned SMTP is a fixed format standardized in advance, the command data format is stored and the format of the acquired IP data packet is stored. It may be determined that it is related to the electronic mail if it matches if it matches the format.

The proxy S receives an IP data packet transferred by the communication library T as instructed by the network driver unit N (Step 5 in FIG. 3). In this case, since the IP data packet includes data and commands related to e-mail, a response signal transmission process is sequentially executed according to the SMTP communication procedure shown in FIG. 4 (Step 6 in FIG. 3).
The transmission process of the response signal by the proxy S is executed by calling the transmission function of the communication library T of the OS, similarly to the transmission process of the e-mail by the mailer M. Interception is also performed for the transmission process (Step 7 in FIG. 3).
In this case, the source IP address of the response signal is the IP address A1 of the computer device itself, and the port number is the port number N1 used by the proxy S. This is because the proxy S executes the transmission process.
Therefore, the network driver unit N notifies the communication library T to rewrite and transfer the IP address A1 and port number N1 to the IP address A2 and port number N2 (usually number 25) of the electronic mail server 2 (see FIG. 3 (Step 8), the communication library T that has received this notification transmits a response signal to the mailer M (Step 9 in FIG. 3).

The transferred response signal is received by the mailer M. The mailer M receives the IP address A2 and the port number N2 of the destination when the mailer M executes the transmission process of the electronic mail (the IP address and the port of the electronic mail server 2). No.) can be received as a response signal from the same IP address and port number. For this reason, the mailer M recognizes as if the electronic mail is transmitted to the electronic mail server 2 and the response signal is received.
In this way, the network driver unit N intercepts and transfers IP data packets related to e-mails sent and received by the mailer M, so that the mailer M can be used without adding special functions or changing settings. No error occurs in the operation of M.
That is, the mailer M can operate regardless of the presence or absence of the electronic mail transmission control program of the present invention.
In addition, since the network driver unit N intercepts emails for all IP data packets that are about to be sent from the computer apparatus 1, it can reliably capture emails regardless of the type of mailer M. It becomes.

  FIG. 5 shows an example of the IP address and port number used in this series of operations.

On the other hand, the proxy S that has received the electronic mail transferred by the network driver unit N notifies the policy determination unit P of the electronic mail. This policy determination unit P is a program that functions as a so-called agent, and refers to policy data PD (which may be acquired from a server device or the like on a network that stores policy data) stored in the hard disk 112 in advance. Make a decision on the email.
For example, if a policy is defined to prohibit sending email to a specific email address, it can be determined whether the destination email address is a prohibited email address or the attached file is encrypted If a policy is set to prohibit sending unsolicited e-mail, it is determined whether or not the attached file is encrypted.

A plurality of policies can be defined in the policy data PD. For example, a policy A that prohibits attachment files, a policy B that prohibits transmission to a specific partner, and an electronic text including a specific character (for example, “secret”) in a mail body Three policies C that prohibit mail transmission can be defined.
When a plurality of policies are included in this way, the policy determination unit P determines whether each policy matches, and notifies the proxy S of the result.

The determination result by the policy determination unit P may be either “permitted” or “discarded” for transmission of the e-mail, or “user determination” is left to determine whether to transmit to the user. It is also possible to choose one of the three options including “wait”. Alternatively, “permission” and “waiting for user judgment” can be selected.
If the determination result of the policy determination unit P is “permitted”, the proxy S that has been notified of the determination information including the determination result sends it directly to the email server 2 without modifying the content of the email. If the determination result is “discard”, the electronic mail is discarded as it is (Step 11 in FIG. 3).
When the determination result is “waiting for user determination”, the user determination input / output unit U is requested to call a GUI for inquiring the user. Specifically, on the GUI, the user is asked to display a screen with a message such as "This email is going to be sent to an email address that is not allowed to be sent as a result of policy judgment. And a determination result input means (button display of “Yes”, “No”, etc.) is displayed.
Then, in response to the result of the user's determination, the policy determination unit P notifies the proxy S of determination information (the process related to the policy determination unit P is Step 10 in FIG. 3).

When the proxy S decides to send the e-mail to the e-mail server 2 as it is, when the proxy S executes the e-mail transmission process (Step 12-1 in FIG. 3), the transmission function of the communication library T is called. Therefore, the network driver N intercepts the e-mail in the same manner as in other cases (Step 12-2 in FIG. 3).
However, in this case, the network driver unit N determines that the combination of the IP address and port number of the intercepted IP data packet is the IP address A1 used when the proxy S performs the transmission process (in FIG. 6, “ 10.0.0.1 ") and the port number N3 (the port number used by the proxy S to send and receive IP data packets to and from the email server 2 and" 9000 "in FIG. 6) Without processing (without rewriting data), transmission is permitted as it is (through transmission) (Step 12-3 in FIG. 3). Then, the communication library T transmits this e-mail (Step 12-4 in FIG. 3).
This is because if the network driver section N intercepts this e-mail and forwards it to the proxy S, it becomes so-called loopback and cannot send the e-mail to the e-mail server 2 ( Step 12 is a series of processes when it is determined in Step 11 that the electronic mail is not discarded.

  In order to distinguish whether an e-mail intercepted by the network driver N is sent from the proxy S to the e-mail server 2 or sent from the mailer M to the e-mail server 2, as described above. If the proxy S is notified in advance of the transmission port number N3 used when the proxy S performs the transmission process, and the source port number of the intercepted e-mail matches the source port number N3 of the proxy S, What is necessary is just to recognize that the proxy S is a transmission source, and the mailer M is a transmission source otherwise.

  FIG. 6 shows an example of the IP address and port number used in this series of operations.

In this example, the policy determination unit P determines whether to permit or cancel the transmission of the e-mail, and then notifies the proxy S of the determination result. It is also possible to notify only the determination result as to whether or not the policy matches the policy, and determine whether to permit or discard the transmission of the e-mail on the proxy S side that has received the determination result I do not care.
For example, when the policy data includes three policies, policy A, policy B, and policy C, the policy determination unit P notifies the proxy S only of the result of whether or not it matches each policy. The proxy S may determine whether to permit transmission of an electronic mail after comprehensively determining whether the proxy S matches each of the three policies.
For example, when the proxy S determines to discard the e-mail only when two or more policies are matched, the policy determination unit P does not match the policy A, but the policy B When the determination result that it matches with the policy C is received, the proxy S decides to discard the e-mail because it matches two or more policies, and the policy A and policy B are determined from the policy determination unit P. If it is determined that the policy C does not match the policy C but only one policy is met, the proxy S may decide to permit transmission of the e-mail. .
In addition, in order to shorten the processing time, priorities are set for a plurality of policies, and it is determined whether or not the policies are matched in order from the policy with the highest priority (for example, policy A). If it is determined that the policy matches the higher policy, the determination is aborted at that point (without determining the other low priority policies), and the determination result indicates that the policy matches the higher priority policy. Alternatively, a method may be used in which only the proxy S is notified.

  That is, the policy determination unit P only needs to transmit determination information, which is information that can be used to determine whether the proxy S permits or discards the transmission of the electronic mail, to the proxy S. It is not necessary to determine whether or not to permit transmission of e-mail.

As described above, the proxy S determines whether to discard or transmit the e-mail according to the determination result by the policy determination unit P, but when transmitting the e-mail, it is necessary to perform special notification to the user. There is no. This is because it is sufficient for the user to execute an e-mail transmission process in the mailer M and find out that the process has been completed without error.
On the other hand, when the proxy S discards the e-mail, it is desirable to notify the user in some way. This is because the user has executed the e-mail transmission process with the mailer M and is sure that the e-mail has been transmitted without error.

Therefore, when the proxy S discards the email according to the determination result notified from the policy determination unit P, the proxy S may newly create a discard notification email indicating that the email has been discarded. The destination e-mail address of the discard notification e-mail is the e-mail address used by the user (the e-mail address of the discarded e-mail). It is desirable for the proxy S to send the e-mail for discard notification to the e-mail server 2 (Step 13-1 in FIG. 3).
In this case as well as the response signal, the network driver N intercepts the discard notification e-mail (Step 13-2 in FIG. 3), but the discard notification e-mail is sent to the IP address of the transmission source. Since the port numbers are the IP address A1 and the port number N3 of the proxy S, they are transmitted as they are (Steps 13-3 and 4 in FIG. 3).
In this way, the mailer M can receive the discard notification email from the email server 2 (Step 13 is a series of processes when it is determined in Step 11 to discard the email).

Note that it is desirable to quote the contents of the email body of the discarded email in the body of the email for notification of destruction. This is to inform the user which electronic mail was the subject of the discard.
Also, the reason for discarding should be described in the text. This is because, when the user re-edits and transmits the e-mail, if the reason for the discard can be referred to, the e-mail can be re-transmitted after the reason is resolved.
Further, the value of “Message-Id” stored in the header area of the discarded email in the header area of the discard notification email (for example, the “In-Reply-To” or “References” area). You may make it transcribe. In this way, when the mailer M is operated to sort sent / received e-mails, the discarded sent e-mail and the e-mail for discard notification are in a continuous positional relationship. Can be easily confirmed and is convenient.

[Contrast with comparative example]
It is not a method of providing the proxy server function unit S on the client device side as in the present invention, and it is determined whether the electronic mail acquired by the network driver unit N matches the policy. A method of transmitting to the mail server device and determining whether to discard or to transmit to the user is also conceivable. That is, the proxy server function unit S is not provided on the client device side.
However, if such a method is adopted, if it is desired to entrust the user with the decision of whether or not to send an e-mail, the communication procedure between the e-mail sending program and the e-mail server device is stopped halfway, and the user makes a decision. Therefore, an error such as a transmission timeout may occur in the SMTP communication procedure or the TCP / IP communication layer while the user is at a loss.
That is, there is a disadvantage in that it does not work well unless the user determines in a short time whether or not to send an e-mail.
Further, if communication with an e-mail transmission program or an e-mail server device is forcibly interrupted, a heavy load is imposed on the e-mail server device that performs communication with a large number of client devices. End up.
Thus, a mechanism that affects the operation of the e-mail transmission program or the e-mail server device is not very desirable.
In this respect, in the present invention, since the proxy server function unit S is provided on the client device side, the communication process is automatically performed in a short time so that no error occurs in the e-mail transmission process itself executed by the mailer M. Can be completed.

As a modification of the present invention, the proxy server function unit S that has received the e-mail intercepted and transferred by the network driver unit N sends an electronic message to the user before sending a response signal to the e-mail transmission program. Another possible method is to determine whether or not to send mail.
Although this method has a demerit that the user has to make a determination in a short time as in the comparative example (because communication of the mailer M is interrupted in the middle), a proxy server function unit S is provided on the client device side. Therefore, the communication of the electronic mail server 2 is not interrupted, and the electronic mail server 2 can be prevented from being loaded.

[Contrast with other comparative examples]
When the proxy server function unit S is provided on the client device side, the IP address of the proxy server function unit S is set to the IP address of the mail server specified in the e-mail transmission program without providing the network driver unit N as in the present invention. A method of setting the address (the address of the client device itself) to operate is also conceivable.
In other words, a proxy server function unit S is provided between the mailer M and the electronic mail server 2 to relay electronic mail, and the other server to which the mailer M directly transmits electronic mail operates on the same client device. The proxy server function unit S is used.
However, this method is troublesome in that the setting of the e-mail transmission program must be changed along with the installation of the e-mail transmission control program.
In particular, when a plurality of users install and operate a plurality of types of e-mail transmission programs on a single client device, it is necessary to change the settings for each e-mail transmission program, resulting in a large amount of labor. turn into.
In addition, when the e-mail transmission control program is uninstalled, the setting of the e-mail transmission program is changed again, and the e-mail address is changed unless the IP address of the designated mail server is reset to the IP address of the e-mail server 2. There is a problem that transmission becomes impossible, which affects settings of programs other than the e-mail transmission control program.
In that respect, according to the present invention, by providing the network driver unit N together with the proxy server function unit S in the client device, it is possible to realize a mail erroneous transmission preventing function without changing the setting of the mailer M. Become.

  Thus, the technical effect of the present invention is realized for the first time by providing the network driver unit N together with the proxy server function unit S in the same computer device as the computer device on which the mailer operates. It is unique and remarkable in that it can solve all the problems that occur.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Computer apparatus, 101 CPU, 111 Memory, 112 Hard disk, 121 Communication interface, 2 E-mail server M E-mail transmission program, N network driver part, S proxy server function part, P policy judgment part, PD policy data, U user judgment Input / output unit, T TCP / IP communication library

Claims (7)

To operate a computer device equipped with an e-mail transmission program for operating a computer device as an e-mail creation / transmission unit for creating and transmitting an e-mail as a network driver unit, a proxy server function unit, and a policy determination unit E-mail transmission control program
The network driver unit is
Interruption means for interrupting transmission of an IP data packet to be transmitted outside the computer device;
Determining means for determining whether the IP data packet is an email;
If the result of the determination is an email, the destination IP address of the IP data packet is set to the IP address of the computer device, and the destination port number is set to the port number used by the proxy server function unit. A delivery means for delivering,
The proxy server function unit
Email notification means for notifying the policy determination unit that an email has been received from the network driver unit;
Determining means for determining discard or transmission of the e-mail based on determination information from the policy determination unit;
The policy determination unit
An acquisition means for acquiring policy data;
A determination unit that determines whether or not the email notified from the proxy server function unit matches a condition defined in the policy data;
An e-mail transmission control program, comprising: information notifying means for notifying the proxy server function unit of determination information according to the determination result. The network driver unit is
When the e-mail is delivered to the proxy server function unit, a response signal indicating that the e-mail has been received is set, the return source IP address is set to the IP address of the e-mail server device, and the return source port number is set to the electronic server. The e-mail transmission control program according to claim 1, further comprising means for setting the port number of the mail server device and sending it to the e-mail creating / transmitting unit. The e-mail transmission control program is:
A program for operating the computer device as a discard notification function unit,
The destruction notification function part
When the proxy server function unit discards the email, means for creating a discard notification email in which the source email address of the discarded email is set as the destination email address;
The e-mail transmission control program according to claim 1, further comprising means for sending the e-mail for discard notification to the e-mail server device.   The e-mail transmission control program according to claim 3, wherein the discard notification e-mail includes a reason why the e-mail is discarded. The policy determination unit
It has a display means for displaying to accept input from the user,
The display means is
When the e-mail notified from the proxy server function unit matches the condition defined in the policy data, display by the display means,
The information notification means includes
The e-mail transmission control program according to any one of claims 1 to 4, wherein information corresponding to an input from a user received by the display unit is included in the determination information. To operate a computer device equipped with an e-mail transmission program for operating a computer device as an e-mail creation / transmission unit for creating and transmitting an e-mail as a network driver unit, a proxy server function unit, and a policy determination unit The operation method of the computer device using the electronic mail transmission control program of
The network driver unit is
Interrupting transmission of an IP data packet to be transmitted outside the computer device;
Determining whether the IP data packet is an email;
If the result of the determination is an email, the destination IP address of the IP data packet is set to the IP address of the computer device, and the destination port number is set to the port number used by the proxy server function unit. Execute the sending step,
The proxy server function unit
Notifying the policy determination unit that an e-mail has been received from the network driver unit;
According to the determination result of the policy determination unit, executing the step of determining to discard or send the e-mail,
The policy determination unit
Obtaining policy data; and
Determining whether the e-mail notified from the proxy server function unit matches a condition defined in the policy data;
And a step of notifying the proxy server function unit of a result of the determination. A computer device for e-mail transmission control, comprising an e-mail creation and transmission unit for executing e-mail creation and transmission, a network driver unit, a proxy server function unit, and a policy determination unit,
The network driver unit is
Means for interrupting transmission of an IP data packet to be transmitted outside the computer device;
Means for determining whether the IP data packet is an email;
If the result of the determination is an email, the destination IP address of the IP data packet is set to the IP address of the computer device, and the destination port number is set to the port number used by the proxy server function unit. Means for delivering,
The proxy server function unit
Means for notifying the policy determination unit that an e-mail has been received from the network driver unit;
Means for determining whether to discard or send the e-mail according to the determination result of the policy determination unit,
The policy determination unit
Means for obtaining policy data;
Means for determining whether or not the e-mail notified from the proxy server function unit matches a condition defined in the policy data;
And a means for notifying the proxy server function unit of the result of the determination.

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