JP3868258B2 - E-mail delivery server - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an e-mail delivery server, and is suitable for use in, for example, delivering e-mail over the Internet according to a procedure according to SMTP performed between sendmails.
[0002]
[Prior art]
Conventional techniques related to e-mail include those described in the following documents 1 and 2.
[0003]
Reference 1: Japanese Patent Laid-Open No. 2001-175552
Reference 2: JP 2001-94589 A
With the spread of mobile phones that can handle e-mails and the development of computer networks such as the Internet, opportunities to use e-mails as information transmission means are increasing. In the business field, the role and distribution volume of e-mail has been increasing year by year. To check e-mail outside the company, e-mail addressed to the company's e-mail address is transferred to a mobile phone or home PC (personal computer). And so on.
[0004]
However, when sending and receiving e-mails via the Internet, there is a risk that the contents will be read and secret information leaked. Furthermore, when the delivery destination is a mobile terminal such as a mobile phone, there are restrictions such as a low processing capacity of the terminal, a low data communication speed, and a high communication cost. For this reason, both the desire to check e-mail easily outside the company and the prevention of leakage of confidential information have been issues.
[0005]
Under such circumstances, the document 1 discloses a system that transmits a summary text of an electronic mail and a ciphertext as a set. When encrypted mail is used, there is a problem that the calculation amount of encryption and decryption is large. However, in Reference 1, the number of encrypted mails that need to be decrypted is reduced by adding a summary sentence. Specifically, a sending client that sends an e-mail including confidential information encrypts the entire e-mail and generates a summary sentence indicating the outline of the e-mail in consideration of not including the confidential information. Attach the full text of the ciphertext to the summary text.
[0006]
The receiving client that has received this can first read the summary text, decrypt only the necessary mail, and read the full text. In other words, the receiving client does not need to decrypt the ciphertext for the less important e-mail. In this way, processing of the receiving client is reduced while ensuring confidentiality.
[0007]
Further, the document 2 discloses a system in which a mail server has a filtering function and an intermediary function. There is a problem that the load on the receiving client becomes heavy when a large amount of e-mails are delivered. However, in Reference 2, the load on the receiving client is reduced by discarding low-importance e-mails at the mail server.
[0008]
Specifically, an e-mail discard condition is set on the mail server, and an e-mail that does not apply to the discard condition is notified. Whether the mail is received or not is consulted with the receiving client or delivered. In addition, mobile telephones are cited as an effective application field of this system.
[0009]
[Problems to be solved by the invention]
However, when using encrypted mail as in Document 1, it is necessary to prepare tools between clients for encryption and decryption, and it is necessary to obtain an ID from a certificate authority (CA) for key management. It was not easy. For this reason, in an in-house network where security is ensured, there are many cases where even e-mails containing confidential information are not encrypted, and forwarding e-mails to company e-mail addresses outside the company is an information leak. It was very dangerous.
[0010]
This may be dealt with by encrypting the e-mail when it is forwarded outside the company, but this is a problem when the e-mail delivery destination is a mobile phone or the like. This is because even if the encrypted mail is delivered to the mobile phone, the mobile phone itself does not support the encrypted mail due to the processing load and cannot be decrypted.
[0011]
The method of delivering summary text and cipher text as described in Document 1 delivers cipher text that may not be decrypted in advance, and therefore wastes communication time and communication cost. Furthermore, since it is necessary for the receiving client to spool the mail composed of the cipher text and the summary text, there is a problem that a memory having a larger capacity than usual is required.
[0012]
In particular, when the receiving client is a mobile phone, the encrypted mail cannot be decrypted, and the number of characters increases by the amount of the summary text. Therefore, there is a possibility that normal reception cannot be performed due to the restriction on the number of characters received in the email. As an example, in the case of a mobile phone network that currently accommodates the largest mobile phone users in Japan, the upper limit of the number of received characters is 250 characters.
[0013]
The system described in Document 2 is intended to prevent delivery of low-priority e-mail such as direct mail, and the load on the receiving client is reduced, but confidentiality is not considered. For this reason, if the system of Document 2 tries to secure confidentiality, the electronic mail is not delivered to the Internet, and the request to check the electronic mail outside the company cannot be met.
[0014]
As described above, in the electronic mail system, both the realization of the desire to easily read electronic mail via the Internet and the countermeasures against information leakage due to the delivery of electronic mail including confidential information are the methods described in Documents 1 and 2. It was not realized by.
[0015]
[Means for Solving the Problems]
In order to solve such a problem, in the present invention, in an electronic mail delivery server that receives an electronic mail to be delivered and delivers the electronic mail according to a predetermined delivery protocol, (1) a header part or a body part of the electronic mail The confidentiality required for the email based on the content of High and low Determine At the same time, if the confidentiality is high, the level of confidentiality is determined. Confidentiality determination means; (2) (3) the summary sentence generation means for generating a summary sentence with a smaller amount of information as the level of confidentiality is higher, with respect to the electronic mail that the confidentiality determination means determines to have high confidentiality; Confidentiality judging means The secret An e-mail that is determined to have low secrecy is delivered as it is according to the delivery protocol, and for an e-mail that is determined to have high secrecy, the e-mail delivery server receives the e-mail after waiting for delivery. To the email recipient In addition, the summary sentence generated by the summary sentence generation means is added. A notification mail delivery control means for delivering the notification e-mail according to the delivery protocol; (4) Delivery standby mail processing means is provided for processing an electronic mail waiting for delivery in accordance with a predetermined delivery standby mail processing procedure executed in accordance with an instruction from a transmission destination.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(A) Embodiment
Embodiments of an electronic mail delivery server according to the present invention will be described below.
[0017]
A mail server (MTA) is an important element that constitutes an e-mail system together with an e-mail transmission source and a destination mailer (MUA). The mail server can be functionally divided into a mail delivery server and a mail receiving server.
[0018]
Among these, the mail delivery server is a server that delivers e-mail according to a mail delivery protocol such as SMTP, and the mail receiving server stores the received e-mail in the received mailbox and uses it as a mail retrieval protocol such as POP3 and IMAP4. Therefore, it is a server that processes the e-mail in the received mailbox in accordance with an instruction from the mailer that is the destination of the e-mail.
[0019]
The mailer is software for sending an e-mail to be sent to a mail delivery server, reading out an incoming e-mail from a receiving mailbox in the mail receiving server, and opening and reading it. It can be mounted on a user terminal such as a mobile phone or a personal computer.
[0020]
There are various methods for delivery of e-mail, but what is usually used on the Internet is to obtain the IP address of the destination by inquiring a DNS server located in the destination domain, and to send the source domain This is a method of delivering directly from a mail delivery server in to a mail receiving server in a destination domain. Since SMTP is positioned in the session layer and the presentation layer of the OSI reference model, it is natural that each protocol below the transport layer such as the TCP / IP protocol is used for this delivery.
[0021]
In this method, the delivery of the e-mail is completed when the e-mail is received by the mail receiving server and stored in the corresponding receiving mailbox, but this is not necessarily the case when the destination is a mobile phone or the like. If it is confirmed that the destination mobile phone is available, delivery may be completed by sending an e-mail led by the mail receiving server.
[0022]
This is because the e-mail system on the cellular phone network is not necessarily the same as a general e-mail system on the Internet. It is considered that what kind of e-mail system is built on the mobile phone network is basically the freedom of the mobile phone operator who manages and operates the mobile phone network. In this case, there is a high possibility that the connection with the e-mail system on the Internet cannot be performed normally. Therefore, even on the cellular phone network, an e-mail system that is basically the same as or similar to the Internet is available. Built.
[0023]
(A-1) Configuration of the first embodiment
A configuration example of a main part of the electronic mail system 10 according to the present embodiment is shown in FIG.
[0024]
In FIG. 1, the electronic mail system 10 includes an intranet 101 and the Internet 102, and a mail server 106 that is a feature of this embodiment is arranged on the intranet 101. In addition, client terminals 103 and 104 are connected to the intranet 101, and client terminals 105 and 120 are connected to the Internet 102.
[0025]
Of course, on the Internet 102 and the like, a number of routers (not shown) for supporting the delivery of electronic mail according to the above-described SMTP are naturally arranged.
[0026]
Among the client terminals 103 to 105, the client terminals 103 and 104 in the intranet 101 may be personal computers equipped with mailers. The client terminal 105 connected to the Internet 102 may also be a personal computer or the like, but here, a mobile phone equipped with a mailer is mainly assumed. When the client terminal 105 is a mobile phone, a mobile phone network PN1 indicated by a dotted line is interposed between the client terminal 105 and the Internet 102.
[0027]
The user U1 who operates the client terminal 103, the user U2 who operates the client terminal 104, and the user U3 who operates the client terminal 105 may be employees of the same company, for example. In this case, the positions of the users U1 and U2 are limited to the inside of the company, but the position of the user U3 may be inside or outside the company.
[0028]
All communication devices existing on the intranet 101 including the mail server 106 and the client terminals 103 and 104 are basically protected by a firewall (not shown). That is, the firewall is set so that an unspecified communication device on the Internet 102 cannot directly access the communication device in the intranet 101 using an unspecified protocol. For this reason, for example, when an electronic mail is exchanged between the client terminals 103 and 104, even if the electronic mail is transmitted and received in plain text, a third party on the Internet 102 may know the contents of the electronic mail. There is no.
[0029]
In order to improve security, a public segment (unarmed segment (DMZ)) may be provided on the intranet 101 to divide the intranet 101 into a public segment and a private segment.
[0030]
The public segment is not completely defenseless in the sense that it is not accessed by an unspecified protocol from an unspecified number of communication devices on the Internet 102 by the access control provided by the firewall, but it is set in the firewall in advance. Access from a limited communication device (or from an unspecified number of communication devices by a limited protocol), compared to communication devices in a private segment, from the Internet 102 Vulnerable to attacks and eavesdropping.
[0031]
As will be described later, the mail server 106 according to the present embodiment needs to receive the reply mail RM1 from the client terminal 105. Therefore, it is necessary to enable at least access from the Internet 102 using SMTP by some method. is there.
[0032]
As an example, an external mail server is arranged on the public segment, and an internal mail server (for example, between the client terminals 103 and 104 is used for in-house electronic mail exchange on the private segment. When the mail server 106 is allocated on the public segment as an external mail server, the reply mail RM1 can be received.
[0033]
When the above-described method for inquiring an IP address to the DNS server is also used for delivery of the reply mail RM1, an external DNS server on the public segment (that is, only a domain name that may be referred from outside the company) (DNS server that has registered) is also required to be arranged. At present, there are almost no cellular phone mailers or e-mail systems that support the Reply-to function, so the e-mail address MA2 of the sender (in the above-mentioned Internet 102) is displayed in the Reply-to field of the notification mail NM1. All e-mails sent to the communication devices in the private segment are once received by the mail server 106) or when the e-mail address of the mail server 106 cannot be written and the user U3 creates the reply mail RM1 In addition, when the e-mail system delivers the reply e-mail RM1 to the mail server 106, the user U3 and the e-mail system need to execute the same procedure as that for creating and delivering a normal new e-mail. It is.
[0034]
In the following description, it is assumed that the electronic mail EM1 is transmitted from the client terminal 104 to the client terminal 105. Further, it is assumed that the e-mail address of the client terminal 104 is MA2, and the e-mail address of the client terminal 105 is MA3.
[0035]
The mail server 106 in FIG. 1 mainly functions as the above-described mail delivery server, has a function of determining the necessity of concealing the original electronic mail to be delivered (here, EM1), and is judged as a mail to be concealed. In this case, the client terminal (105 in this case) is notified of the arrival of the e-mail that should be kept secret before the e-mail is delivered. In order to realize such a function, the mail server 106 includes a mail server unit 107, a notification mail generation unit 108, a confidentiality necessity determination unit 109, a delivery mail selection unit 110, and a control unit 111. Yes.
[0036]
Of these, the mail server unit 107 is basically a part realized by a server application program such as sendmail in the UNIX (registered trademark) system. Sendmail, which is a mail transfer agent (MTA), is not limited to the UNIX (registered trademark) system, and various programs already exist, but most of them are electronic so that electronic mail can be exchanged between various computers. It usually has only the minimum functions necessary for mail delivery and does not have an authentication function.
[0037]
Since a normal mail delivery server has only a function corresponding to the mail server unit 107, it can be said that the feature of the present embodiment is the constituent elements 108 to 111 other than the mail server unit 107.
[0038]
However, when a normal sendmail receives a certain e-mail, the mail server 107 according to the present embodiment only performs delivery of the e-mail through a procedure such as inquiring the IP address of the DNS server. The received e-mail is not immediately delivered, but is first supplied to the confidentiality determination unit 109, the notification e-mail generation unit 108, and the delivery e-mail selection unit 110, and the e-mail selected by the delivery e-mail selection unit 110 is sent according to SMTP. It must be delivered to the next mail server.
[0039]
Further, when the electronic mail to be delivered is not the original electronic mail EM1 but the notification mail NM1, the original electronic mail EM1 needs to be stored in the mail box BX1 or the like after the notification mail NM1 is delivered.
[0040]
As an example, when the mail server 106 receives an e-mail (for example, EM1), the e-mail is not passed to the sendmail in the mail server unit 107, but the confidentiality necessity determination unit 109, the notification mail generation unit 108, and the delivery If the configuration is such that the e-mail (EM1 or NM1) output from the delivery mail selection section 110 is delivered to the sendmail (sendmail recognizes the reception of the e-mail for the first time at this point) Since sendmail can be implemented as it is with almost no modification, it is convenient.
[0041]
The notification mail generation unit 108 connected to the mail server unit 107 notifies the destination user U3 that the electronic mail EM1 has arrived at the mail server 106 based on the content of the original electronic mail EM1. In the part for automatically generating NM1, the generated notification mail NM1 is supplied to the delivery mail selection unit 110. The notification mail NM1 has a special meaning for the destination user U3 in that it is used for the purpose of notifying the incoming call. However, the notification mail NM1 is completely normal e-mail when viewed from the e-mail system. Similarly, it is delivered according to SMTP.
[0042]
The notification mail NM1 is delivered in a case where the original e-mail EM1 is highly confidential, so the notification mail NM1 itself should not reveal the contents of the e-mail EM1, but on the other hand, the notification mail NM1 Contains the minimum necessary information about the email EM1, since it is necessary to provide information that is the basis for determining whether the original email EM1 is worth reading for the destination user U3. There is a need. In order to ensure confidentiality, the smaller the amount of information the notification mail NM1 has, the better. However, in order to provide the basis for value judgment, the larger the amount of information, the better. It can be said that it is a difficult and subtle problem that must satisfy the requirements that often contradict each other.
[0043]
As an example, the notification mail NM1 may be generated by extracting information such as the sender (sender) and creation time (transmission time) from the header part of the original electronic mail EM1. For example, “U2-san received a confidential e-mail from XX hour at XX”. However, the generation of the notification mail NM1 is not particularly limited to this method, and information of the mail text may be used. For example, the word “urgent” may be searched from the text, and a message such as “U2 has received a confidential email from XX hour at XX. This email contains the word“ urgent ”.
[0044]
However, if the notification mail generation unit 108 performs complicated processing that makes it difficult for the user U2 to predict the content of the notification mail NM1 that is the processing result, the notification mail NM1 is generated that includes important information that the user U2 wants to keep secret. In general, it is considered that the process performed by the notification mail generation unit 108 should be as simple as possible so that the user U2 can clearly predict the result. .
[0045]
For example, the notification e-mail NM1 having no valid content in the text may be generated simply by using the original e-mail EM1 as the title of the e-mail NM1.
[0046]
Since the title of the e-mail EM1 is created by the user U2 as the sender, an appropriate title that can solve the difficult and subtle problems described above is created, and the notification mail generation unit 108 sends the title as is to the notification mail. If the process of making the title (which may be the text if necessary) and informing the user U2 in advance, the contents of the generated notification mail NM1 can be clearly predicted, The sense of security of the user U2 is also increased.
[0047]
Also, by setting the title of the e-mail EM1 as the title instead of the content of the notification mail NM1, when the client terminal 105 receives the notification mail NM1, the value can be judged without opening it. . Depending on the e-mail system on the cellular phone network PN1, there is a high possibility that downloading of the e-mail EM1 itself is unnecessary when opening is unnecessary, and it is possible to save the limited memory capacity of the cellular phone.
[0048]
Note that each field in the header of an e-mail (EM1, NM1, etc.) usually has a message ID (unique number for distinguishing each e-mail; automatically assigned by the mail server 106), date and time of transmission. , Sender (sender) information (sender's email address (here, MA2) and name), destination information (sender's email address (here, MA3)), email title, email text Each type of information indicating the type (text, image, audio, etc.) is stored.
[0049]
The delivery mail selection unit 110 is a part for selecting a delivery mail from the original electronic mail EM1 or the notification mail NM1 generated by the notification mail generation unit. This selection is executed according to the selection control signal SC supplied from the confidentiality necessity determination unit 109 to the control input terminal.
[0050]
Similar to the notification mail generation unit 108, the confidentiality necessity determination unit 109 that receives the electronic mail EM1 from the mail server unit 107 determines whether the confidentiality of the electronic mail (here, EM1) to be delivered by the mail server 106 is high or low. The selection control signal SC corresponding to the determination result is supplied to the control input terminal of the delivery mail selection unit 110.
[0051]
That is, the confidentiality necessity determination unit 109 outputs a selection control signal SC for selecting the notification mail NM1 when it is determined that the necessity for confidentiality is high, and the original electronic mail when it is determined that the necessity for confidentiality is low. A selection control signal SC for selecting EM1 is output.
[0052]
The electronic mail (EM1 or NM1) selected at this time is delivered to the client terminal 105, which is the transmission destination, in plain text.
[0053]
The concealment necessity determination unit 109 determines the necessity of concealment from the information described in the header part of the received email EM1 and the content described in the text. There are various things.
[0054]
For example, the determination may be made using the transmission source information read from the corresponding field of the header part, the title of the mail, and the extended field information.
[0055]
In this case, as an example, it may be determined that the e-mail from a specific transmission source is concealed, and if the title includes characters such as “confidential”, it is concealed. In addition, it is possible to determine the necessity of secrecy by searching for descriptions that indicate secrets such as “limited information” and “confidential” and descriptions that indicate amounts such as “price” and “20.0 billion yen”. is there.
[0056]
However, here too, as with the notification mail generation unit 108, it is possible to give a sense of security if the determination result of the confidentiality determination unit 109 can be predicted by the user U2. This occurred because the e-mail EM1 was sent in the hope that it would be kept secret, but it was not actually kept secret, and the plain-text e-mail EM1 was delivered over the Internet 102 and wiretapped. This is to prevent it from occurring. In this sense, for example, it is desirable that the user U2 can explicitly indicate that the confidentiality is high by describing characters such as “confidential” in the title. In this case, it is natural that it is assumed that the user U2 is informed that the processing is performed with high confidentiality if characters such as “confidential” are described in advance in the title.
[0057]
Note that the notification mail NM1 is not necessary when the concealment necessity determination unit 109 determines that the confidentiality of the electronic mail EM1 is low, and therefore, only when the concealment necessity determination unit 109 determines that the concealment is high. It is efficient if the notification mail generation unit 108 is configured to generate the notification mail NM1.
[0058]
Finally, the control unit 111 determines the process for the electronic mail EM1 when it is determined that the confidentiality is high according to an instruction from the user U3 of the transmission destination who has read the notification mail NM1, and responds to the determination. This is the part that executes processing.
[0059]
At least a part of the processing content related to the e-mail (for example, EM1) determined to be highly confidential may be registered in advance for each transmission destination user, or all of the processing content may be stored in the transmission destination user. It may be determined dynamically according to a reply mail (for example, RM1) from (for example, U3).
[0060]
When the client terminal 105 is a mobile phone, for example, the e-mail EM1 encrypted by an e-mail encryption method such as the most popular S / MIME or the well-known PEM or PGP is decrypted. Therefore, it may be transferred to the client terminal 120 installed at the home of the user U3 and read at home. The client terminal 120 is not a mobile phone or the like, but a communication device equipped with a mailer having a decoding function corresponding to S / MIME, PEM, PGP, etc., and may be a personal computer, for example.
[0061]
In this case, the e-mail address MAX or the like of the client terminal 120 at home may be registered in advance in the control unit 111 or the like in the mail server 106, or may be dynamically instructed by the reply mail RM1. If it is registered in advance, the reply mail RM1 only needs to specify whether transfer is necessary.
[0062]
When the e-mail EM1 is transferred to the client terminal 120 at home, the e-mail EM1 is accommodated in the header portion of the original e-mail EM1. Re The control unit 111 executes a process of rewriting the e-mail address MA1 that is the destination information to the e-mail address MAX of the client terminal 120 at home, and after performing the encryption, performs delivery according to SMTP There is a need to do. EN (EM1) in FIG. 1 indicates an email obtained by encrypting the email EM1.
[0063]
When the client terminal 105 is a mobile phone that does not have a Reply-to function, it is a problem how the mail server 106 recognizes the correspondence between the original electronic mail EM1 and the reply mail RM1. It becomes. The reply mail RM1, like the notification mail NM1, is a special mail for the user U3. However, the external mail is not different from a normal electronic mail, and the mail server 106 may process it simultaneously with the electronic mail EM1. It is indistinguishable from many other emails.
[0064]
As an example, the reply mail (RM1) is displayed as “reply” in the title of the reply mail (RM1), and the reply mail that may be processed at the same time is identified in the header of the reply mail. Based on the correspondence between the source and destination e-mail addresses (MA3, MA2) included and the destination and source e-mail addresses (MA2, MA3) included in the header of the original e-mail (EM1) May be executed. However, in this case, the mail server 106 can handle only one email (for example, EM1) from the same transmission source (for example, MA2) to the same transmission destination (for example, MA3) at the same time.
[0065]
In order to handle a plurality of e-mails (for example, EM1) from the same source to the same destination at the same time, for example, a reply mail (RM1) including the message ID of the notification mail (NM1) may be transmitted. . Since the message ID is unique to each electronic mail, the message ID (which also stores the correspondence between the message ID and the original electronic mail EM1) is stored in the mail server 106 (control unit 111) when the notification mail is transmitted. If the reply mail arrives, the original electronic mail corresponding to the reply mail can be uniquely identified.
[0066]
In addition to these methods, the transmission destination user U3 obtains the encrypted electronic mail EM1, a method of browsing the mail using a Web browser, the sender U2 of the original mail EM1 (or the mail server 106). For requesting to retransmit the encrypted mail in accordance with the encryption / decryption environment of the receiving client terminal (105 or 120), and for inquiring the sender U2 of the original mail by another means such as a telephone is there.
[0067]
The operation of the present embodiment having the above configuration will be described below. The operation of the mail server 106 of this embodiment is shown in the flowchart of FIG. The flowchart in FIG. 2 includes steps S21 to S26.
[0068]
(A-2) Operation of the first embodiment
Here, for simplicity of explanation, the internal mail server and the external mail server are not separately installed in the intranet 101, but the external and internal mail servers are installed, and the mail server 106 is This dual-purpose mail server is assumed.
[0069]
In addition, it is assumed that the electronic mail EM1 having the same content is transmitted from the client terminal 104 to the client terminals 103 and 105. In such a case, normally, the e-mail address MA1 of the client terminal 103 and the e-mail address MA3 of the client terminal 105 are described in the CC field or BCC field of the header part of the e-mail EM1.
[0070]
In FIG. 2, when the mail server 106 receives the electronic mail EM1 including the secret information from the transmission source client terminal 104, the mail server 106 refers to the description of the CC field or the BCC field of the electronic mail EM1 (S21). ) Recognizes that there is one job delivered to the client terminal 103 in the intranet 101 and another job delivered to the client terminal 105 outside the intranet 101.
[0071]
Since delivery to the client terminal 103 in the intranet 101 is performed by a route closed in the secure intranet 101, step S22 branches to the NO side and delivers the plain text e-mail EM1 to the client terminal 103. (S26), the job is completed.
[0072]
On the other hand, since delivery to the client terminal 105 outside the intranet 101 goes through a dangerous route (in this case, the Internet 102) that may be read, step S22 branches to the YES side, and the necessity of concealment within the mail server 106 is required. The determination unit 109 determines whether or not the confidential information is included in the electronic mail EM1, that is, whether or not the confidentiality is high (S23).
[0073]
If the concealment necessity determination unit 109 gives a determination result that the confidentiality of the electronic mail EM1 is low, step S23 branches to the NO side, and the plaintext is left via the delivery mail selection unit 110. When the electronic mail EM1 is delivered via the Internet 102 (S26), all jobs are completed.
[0074]
However, if it is determined that the confidentiality is high, step S23 branches to YES and the notification mail NM1 generated by the notification mail generation unit 108 is delivered (S24, S25).
[0075]
When the client terminal 105 is a mobile phone, an incoming e-mail to the mail receiving server is immediately notified to the mobile phone user U3 by a ring tone or vibration, so that the e-mail can function as an almost real-time communication means. It is highly likely that the user U3 will read the notification mail NM1 immediately after the NM1 is received.
[0076]
As described above, reception of the reply mail RM1 and transfer of the encrypted electronic mail EN (EM1) corresponding to the contents of the reply mail RM1 can be performed following the delivery of the notification mail NM1. With the transfer of the encrypted electronic mail EN (EM1), all the jobs of the mail server 106 generated by the reception of the electronic mail EM1 are completed.
[0077]
When the in-house mail server and the external mail server are separately installed in the intranet 101, the in-house mail server does not deliver the e-mail addressed to the private segment (for example, the client terminal 103) by itself. The delivery of the e-mail addressed to the outside (for example, the client terminal 105) performed via the Internet 102 is not performed by itself, but the e-mail is transferred to the mail server 106 which is an outside mail server, and then delivered. It is preferable to leave the subsequent processing including the above to the mail server 106.
[0078]
As a result, it is not necessary for the in-house mail server in the private segment to directly receive the reply mail RM1 via the Internet 102, and security can be improved.
[0079]
By the way, since general SMTP does not have an authentication function as described above, it is relatively easy to change the transmission source, etc., and a third party eavesdrops on a notification mail NM1 delivered over the Internet 102 in plain text. There is a possibility that the third party's communication device transmits the encrypted original e-mail EM1, but this problem is caused by a destination registered in advance by the mail server 106. This can be dealt with by transferring the e-mail EM1 only to the mail address and not transferring it to any other destination.
[0080]
At present, most mobile phones cannot read attached files (word processor document files, image files, etc.) attached to e-mails. However, if this embodiment is used, a personal computer (120) as a transfer destination, etc. It is also possible to read the attached file.
[0081]
That is, the transfer to the client terminal 120 can be used as a means for reading the attached file of the email EM1. In this case, the notification mail NM1 may be used to notify the presence / absence of an attached file.
[0082]
(A-3) Effects of the first embodiment
According to the present embodiment, encrypted email is delivered only when the destination user recognizes that it is necessary, thus saving communication time and cost and maintaining the confidentiality of the email. However, it is possible to easily read e-mails via the Internet.
[0083]
In addition, since the email is encrypted only when necessary according to the route of delivery of the email, the content of the email, and the intention of the destination user, the overall flexible and efficient email A system can be provided.
[0084]
Furthermore, since the notification mail (NM1) for notifying the destination user of the arrival of the e-mail (EM1) is a plain text e-mail having a small size, it can be easily read by a mobile phone or the like, and the storage capacity consumed at that time Can also save.
[0085]
(B) Second embodiment
Below, only the point from which this embodiment is different from 1st Embodiment is demonstrated.
[0086]
This difference is mainly limited to the fact that an outline is added to the notification mail.
[0087]
(B-1) Configuration and operation of the second embodiment
FIG. 3 shows a configuration example of a main part of the electronic mail system 11 according to the present embodiment.
[0088]
In FIG. 3, the function of the component which attached | subjected the code | symbol same or corresponding to FIG. 1 is fundamentally the same as 1st Embodiment. That is, the intranet 301 is the same as the 101 and the Internet 302 is the same as the 102, the client terminal 303 is the 103, the client terminal 304 is the 104, the client terminal 305 is the 105, and the client terminal 320 is the 120. The same.
[0089]
Further, the function of the mail server 306 basically corresponds to the mail server 106, in which the mail server unit 307 is the 107, the notification mail generation unit 308 is the 108, and the confidentiality necessity determination unit 309 is the 109, the delivery mail selection unit 310 corresponds to the 110, and the control unit 311 corresponds to the 111.
[0090]
Further, each signal and information given the same reference numerals as those in FIG. 1 and users, that is, MA1 to MA3, MAX, EM1, NM1, RM1, SC, and EN (EM1) are the same as those in the first embodiment.
[0091]
The summary sentence generation unit 312 in the mail server 306, which is a newly added component in the present embodiment, is a part that automatically creates a summary sentence AB1 related to the contents of the email EM1 based on the email EM1. The generated summary sentence AB1 is output to the notification mail generation unit 308.
[0092]
The notification mail generation unit 308 that has received the summary sentence AB1 is a part that generates and outputs a notification mail NM11 with a summary sentence by adding the summary sentence AB1 to the notification mail NM1 generated within itself. . Here, the output notification mail NM11 with the summary sentence is handled in the mail server 306 in the same manner as the notification mail NM1 of the first embodiment.
[0093]
The addition method may be, for example, a form in which the description of the content of the summary sentence AB1 is added to the body part of the notification mail NM1 (including the case where the notification mail NM1 does not have valid contents in the body part).
[0094]
The summary sentence AB1 describes the contents of the e-mail EM1 in more detail than the notification mail NM1 of the first embodiment, but reveals the part to be concealed in the contents of the original e-mail EM1. (If the main point of the context of the text itself is a matter that should be kept secret, the main point should not be disclosed. Therefore, in this case, a so-called "outline" is described in a form that can be understood by anyone. This point is the same as the notification mail NM1.
[0095]
Further, since the summary sentence AB1 is added to the notification mail NM1, if it is the same as the content of the notification mail NM1, its meaning is lost.
[0096]
For example, a notification e-mail including a sentence “A confidential e-mail has arrived from Mr. U2 at the time of XX” in the body part using information such as the sender and creation time included in the original mail EM1. If NM1 is generated, an outline-sent notification mail NM11 can be generated by adding a sentence "The outline of this mail is as follows. <Contents of summary sentence AB1>".
[0097]
For the generation of the summary sentence AB1, a statistical method for extracting sentences containing frequently occurring characters in the e-mail EM1, and the main points of the mail EM1 such as questions, reports, and requests are judged and the sentences according to the main points are extracted. It is also possible to use various methods, such as a method to do.
[0098]
The operation of the mail server 306 according to the present embodiment is as shown in the flowchart of FIG. 4 composed of steps S41 to S46. As is apparent from a comparison between FIG. 4 and FIG. 2 which is the flowchart of the first embodiment, the only difference between the two is the presence or absence of the outline sentence generation process performed in step S44.
[0099]
The outline sentence generation process is a process executed by the outline sentence generation unit 312.
[0100]
Note that when the confidentiality determination unit 309 determines that the confidentiality of the electronic mail EM1 is low, the notification mail NM1 itself is not required, so that it is not necessary to generate the summary sentence AB1 to be added thereto, and can be omitted. It is.
[0101]
(B-2) Effects of the second embodiment
According to this embodiment, it is possible to obtain an effect equivalent to the effect of the first embodiment.
[0102]
In addition, in this embodiment, since a summary sentence is added to the notification mail, more information that is the basis of value judgment can be provided, and convenience for the transmission destination user (U3) is improved.
[0103]
(C) Third embodiment
In the following, only the differences of the present embodiment from the first and second embodiments will be described.
[0104]
This difference is mainly that when there is a high need for secrecy, detailed processing is performed according to the height. Nikka I can be cut off.
[0105]
(C-1) Configuration and operation of the third embodiment
FIG. 5 shows a configuration example of a main part of the electronic mail system 12 according to the present embodiment.
[0106]
In FIG. 5, the function of the component which attached | subjected the code | symbol same or corresponding to FIG. 1 is fundamentally the same as 1st Embodiment. That is, the intranet 501 is the same as the 101 and the Internet 502 is the same as the 102, the client terminal 503 is the 103, the client terminal 504 is the 104, the client terminal 505 is the 105, and the client terminal 520 is the 120. The same.
[0107]
The function of the mail server 506 basically corresponds to the mail server 106, in which the mail server unit 507 is the 107, the notification mail generation unit 508 is the 108, and the confidentiality necessity determination unit 509 is the 109, the delivery mail selection unit 510 corresponds to the 110, and the control unit 511 corresponds to the 111.
[0108]
Further, each signal and information given the same reference numerals as those in FIG. 1 and users, that is, MA1 to MA3, MAX, EM1, NM1, RM1, SC, and EN (EM1) are the same as those in the first embodiment.
[0109]
The function of the summary sentence generation unit 512 assigned with the reference numerals corresponding to those in FIG. 5 corresponds to the summary sentence generation unit 312 of the second embodiment, but depends on the signal LB supplied from the confidentiality necessity determination unit 509. It has a function to generate summary sentences.
[0110]
The concealment necessity determination unit 509 includes a concealment level determination unit 513 as shown in FIG. The secrecy level determination unit 513 is a part that operates when the secrecy of the original electronic mail EM1 is determined to be high. The secrecy level that is determined to be high is described in more detail. Judging.
[0111]
The details of the determination of the confidentiality level may be any number of levels as long as it is two or more, but here, as an example, it is assumed that the determination is made in three levels of high, medium, and low.
[0112]
Further, for the determination of the level of secrecy, for example, a method of determining from characters such as “most important secret”, “important secret”, “confidential” described in the original e-mail EM1, or a method of determining from the title of the sender Etc.
[0113]
When the concealment level determination unit 513 determines the concealment level, a concealment level signal LB corresponding to the determination result is supplied from the concealment necessity determination unit 509 to the summary sentence generation unit 508.
[0114]
Then, the summary sentence generation unit 508 that has received the secret level signal LB generates a different summary sentence AB11 according to the content of the secret level signal LB. In general, the higher the secrecy level indicated by the secrecy level signal LB, the lower the amount of information that the summary sentence has, and the lower the secrecy level, the greater the amount of information that the summary sentence has. This amount of information is supposed to be the amount of information that is meaningful for the destination user U3 or a third party on the Internet 502 who wants to eavesdrop (the amount of valuable information). For example, if the number of characters is simply used as the amount of information, the general sentence generation unit 512 can be easily processed.
[0115]
When the number of characters is used as a control criterion, it is recognized that the necessity for concealment is high, but the e-mail EM1 with a relatively low level of secrecy increases the number of characters in the summary sentence AB11 and the e-mail with a relatively high level of secrecy For EM1, the number of characters in the summary sentence AB11 is reduced.
[0116]
As an example, the summary sentence AB11 is output so that the secret level is 50 characters when the secret level is high (most important secret), 100 characters when the secret level is medium (important secret), and 200 characters when the secret level is low (normal level). You may do it. The number of characters may be fixed for each concealment level, but can be adaptively increased or decreased according to the number of characters in the body of the original e-mail EM1.
[0117]
Even when the client terminal 505 is a mobile phone, the above upper limit of 250 received characters is the lowest character limit among major mobile phone operators in Japan, and other mobile phone operators Since reception of 2000-character or 3000-character e-mail is permitted, the number of characters for each confidential level listed here is a realistic value applicable to any mobile phone network.
[0118]
A flowchart showing the operation of the mail server 506 of this embodiment is as shown in FIG. The flowchart of FIG. 6 is composed of steps S61 to S68. As is apparent from the comparison with FIG. 2 which is the flowchart of the first embodiment, each of steps other than steps S64 and S65 (S65a to S65c). The steps are the same as in the first embodiment.
[0119]
In step S64, which is executed after it is determined that the confidentiality of the received electronic mail EM1 is high and step S63 branches to the YES side, the confidentiality level determination unit 513 determines the confidentiality level.
[0120]
If the determined secrecy level is high, an approximate sentence AB11 of n characters or less is generated by the approximate sentence generation unit 512 in step S65a. Similarly, if the concealment level is medium, in step S65b, When the summary sentence AB11 of m characters or less is generated and the level of secrecy is low, the summary sentence AB11 of 1 characters or less is generated in step S65c. The magnitude relationship between n, m, and l is n <m <l.
[0121]
In the subsequent step S66, the notice mail with summary sentence NM11 to which the summary sentence AB11 generated here is added is generated.
[0122]
(C-2) Effects of the third embodiment
According to this embodiment, an effect equivalent to the effect of the second embodiment can be obtained.
[0123]
In addition, in the present embodiment, the amount of information of the summary sentence can be finely changed according to the confidentiality level of the original electronic mail (EM1), so that the flexibility is high and the usability is good.
[0124]
(D) Other embodiments
In the above first to third embodiments, if Web mail that reads and writes electronic mail using a Web browser instead of a mailer is used, the contents of the mail text can be described according to a previously created form. The user U2 of the transmission source can also specify in detail a phrase or the like to be concealed regarding the header part and body part of the email EM1. According to this, even if fairly complicated processing is performed with functional blocks corresponding to the notification mail generation unit 108, the summary sentence generation unit 512, and the like, confidentiality can be maintained, and the feeling of security of the transmission source user is increased.
[0125]
In the second and third embodiments, the summary text is added to the notification mail. However, the delivery of the summary text (AB1 or AB11) to the destination user (U3) is the notification mail. You may make it carry out separately. This means that the same method as that for obtaining the original mail (EM1) in the first embodiment is applied to the summary sentence.
[0126]
That is, as in the first embodiment, a notification mail (NM1) without an outline is added to the destination user (U3) first, and the destination user sends the outline mail to the mail server (corresponding to 506). When an outline request mail instructing delivery is sent, the mail server delivers the outline mail.
[0127]
However, since the summary sentence is considered in the generation process, it can be delivered without being encrypted like the original electronic mail (EM1). Therefore, the delivery destination of the summary text mail may be a mobile phone or the like.
[0128]
Moreover, since the intention of the transmission destination user (U3) is reflected in the delivery of the summary mail in this method, it can be said that the method is more flexible than the methods of the second and third embodiments.
[0129]
In the above description, the present invention is realized mainly by hardware, but the present invention can also be realized by software.
[0130]
【The invention's effect】
As described above, according to the present invention, the processing of electronic mail in the electronic mail delivery server can be changed according to the confidentiality of the electronic mail to be delivered and the instruction from the transmission destination. Thus, it is possible to save communication time and communication cost, and to maintain the confidentiality of e-mail even when a dangerous delivery route (for example, the Internet or the like) that may be wiretapped is passed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration example of a main part of an electronic mail system according to a first embodiment.
FIG. 2 is a flowchart showing the operation of the first embodiment.
FIG. 3 is a schematic diagram illustrating a configuration example of a main part of an electronic mail system according to a second embodiment.
FIG. 4 is a flowchart showing the operation of the second embodiment.
FIG. 5 is a schematic diagram showing a configuration example of a main part of an electronic mail system according to a third embodiment.
FIG. 6 is a flowchart showing the operation of the third embodiment.
[Explanation of symbols]
10-12 ... E-mail system, 101, 301, 501 ... Intranet, 102, 302, 502 ... Internet, 103-105, 120, 320, 520, 303-305, 503-505 ... Client terminal, 106, 306, 506 ... Mail server, 108, 308, 508 ... Notification mail generation unit, 109, 309, 509 ... Concealment necessity judgment unit, 110, 310, 510 ... Delivery mail selection unit, 111, 311, 511 ... Control unit, 513 ... Concealment Level judgment unit, EM1 ... original email, EN (EM1) ... encrypted email, NM1 ... notification email, NM11 ... notification email with summary text, AB1, AB11 ... summary text.

Claims (5)

In an e-mail delivery server that receives e-mail to be delivered and delivers e-mail according to a predetermined delivery protocol,
With determining the confidentiality of height required for the e-mail based on the contents of the header portion or body portion of the electronic mail, when the high secrecy, confidentiality decision determining the level of confidentiality of height Means,
With respect to the electronic mail that the confidentiality determination means determines to have high confidentiality, an outline sentence generation means that generates an outline sentence with a smaller number of characters as the level of confidentiality is higher;
The secrecy determining means, electronic mail determined the confidentiality is low is delivered according as the delivery protocol, above with respect to the determined e-mail that there is a high secrecy that is waiting for its delivery, the electronic mail Notification mail delivery control for notifying the destination of the e-mail that the e-mail delivery server has received and delivering the notification e-mail to which the summary sentence generated by the summary sentence generation means is added according to the delivery protocol Means,
An e-mail delivery server, comprising: e-mail delivery waiting processing means for processing an e-mail waiting for delivery according to a predetermined delivery e-mail processing procedure executed in accordance with an instruction from a transmission destination. The e-mail delivery server of claim 1,
The confidentiality determination means includes
An e-mail delivery server comprising a body content determination unit that determines the level of confidentiality required of the e-mail according to the content of a lexical phrase included in the body portion of the e-mail. The e-mail delivery server of claim 1,
The confidentiality determination means includes
An e-mail delivery server comprising: a header content determination unit that determines the level of confidentiality required for the e-mail according to the description content of a corresponding field included in the header portion of the e-mail. The e-mail delivery server of claim 1,
The delivery standby mail processing means includes a procedure of encrypting and delivering the electronic mail to a destination designated by the electronic mail transmission destination as a part of the delivery standby mail processing procedure. E-mail delivery server. The e-mail delivery server of claim 1,
The notification mail delivery control means creates the notification e-mail after it is determined that the confidentiality is high.

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