JP2005251230A - Mail server - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively exclude spam mails without requiring troublesome time and effort for a user and without causing a state that it becomes impossible to receive required mails. <P>SOLUTION: A spam mail decision part 17 decides a mail in which the total of the number of local user address used as destination among e-mails whose destinations are decided as local in a transmitting destination decision part 13 and the number of e-mails in which at least one of a transmitting origin, a title and data size is the same as the applicable e-mail among the e-mails stored in a mail storage part 12 becomes a threshold or more as spam mails. A spam mail processing part 18 transmits a confirmation mail whether or not to receive the spam mail to the user for the mail whose address at the transmitting origin is not registered in a decision unnecessary list server 5 among the mails decided as the spam mails by the spam mail decision part 17 and transmits only the one to which a reply mail that it is received is transmitted from the user to a mail box 16. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mail server in an e-mail transfer system that transfers an e-mail from a sender's terminal to a recipient's terminal via a network such as the Internet.

  In recent years, transmission / reception of electronic mail via a network such as the Internet has been widely performed. In addition, since a mobile terminal such as a mobile phone can also send and receive e-mails, e-mails are further sent and received.

  However, so-called junk mail (spam mail) that unilaterally sends e-mail such as direct mail to a large number of unspecified users using the widespread use of e-mail in this way is a problem. . In particular, since the e-mail address of a mobile phone or the like is often used as it is, the e-mail address can be easily predicted by a third party. It has become possible to send spam mail.

  Since it is difficult for a user who has sent such junk mail to determine whether the e-mail is junk mail or normal e-mail, the communication cost for reading the e-mail that has arrived in the mailbox is low. In the case of a burden, the user bears a useless communication cost in order to receive such a junk mail.

  In addition, if the number of junk mails and the amount of packets per one junk mail increase, the amount of packets for receiving such junk mails increases, and it takes time to receive ordinary e-mails. Will be affected. Further, when the communication cost is set according to the price per packet amount, the user bears a useless communication cost in order to receive the junk mail. Furthermore, the received user may become uncomfortable depending on the contents of the spam mail.

  As described above, the spam mail hinders the original convenience of the electronic mail system, and also causes an adverse effect that the user has to bear a wasteful communication cost.

  As a method for preventing such junk mail from being received, in the conventional e-mail transfer system, the address of the sender that the user wishes to refuse is registered, and the e-mail from the registered sender is registered. It is proposed not to deliver to users. The configuration of such a conventional electronic mail transfer system is shown in FIG.

The conventional electronic mail forwarding system, as shown in FIG. 5, and the mail server 20 ₁ to 20 _n functioning as MTA (Message Transfer Agent), and DNS (Domain Name System) server 3, the user terminal 1, It consists of a black list server 4 and user terminals 2 ₁ to 2 ₃ connected to the mail server 20 _n .

Here will be described with reference to the case where e-mail sent from the user terminal 1 connected to the mail server 20 ₁ is transferred to the mail server 20 the user terminal 2 ₁ to 2 ₃ connected to the _n.

The DNS server 3 is a server for converting between a host name and an IP address. Black list server 4, each user of the user terminal 2 ₁ to 2 ₃ is a server for registering in advance the source address to deny reception.

The mail servers 20 _{1 to} 20 _n are devices for delivering electronic mail, and the configuration thereof is shown in FIG. 6 as a representative of the mail server 20 _n .

As shown in FIG. 6, the mail server 20 _n includes a mail reception unit 11, a mail storage unit 12, a transmission destination determination unit 63, a local processing unit 64, a remote processing unit 15, and a mail box 16. It is configured.

The mail receiver 11 receives an electronic mail transmitted from the user terminals 2 ₁ to 2 ₃ or an electronic mail transferred from another mail server. The mail storage unit 12 stores the electronic mail received by the mail receiving unit 11.

Destination determination unit 63 performs determination of the stored in the mail storage unit 12 e-mail address, the user terminal 2 ₁ to 2 ₃ addressed to the destination is connected to its own mail server 20 _n (in this case It is determined whether the destination is local) or the destination is a user terminal other than the user terminal connected to the mail server 20 _n (in this case, the destination is called remote). Then, the transmission destination determination unit 63 transfers the electronic mail whose destination is local to the local processing unit 64 and transfers the electronic mail whose destination is remote to the remote processing unit 15.

The local processing unit 64 performs processing for distributing the electronic mail transferred from the transmission destination determination unit 63 to each of the user terminals 2 ₁ to 2 ₃ by storing it in the mail box 16. The remote processing unit 15 transfers the electronic mail transferred from the transmission destination determination unit 63 to another server. The mailbox 16 is for storing an e-mail for each user, and each user terminal can receive the e-mail by accessing the mail box 16 and reading the stored e-mail. .

  Next, the operation of this conventional electronic mail transfer system will be described.

First, the user terminal 1 transmits an e-mail to the mail server, the mail server 20 _1, based on the information stored in the DNS server 3, converts the destination IP address. The mail server 20 ₁ transmits the e-mail to the mail server 20 ₂ because the e-mail is not addressed to the local user terminal. The operation after the e-mail transferred between the mail servers in this way is transferred to the mail server 20 _n will be described in detail with reference to the flowchart of FIG.

First, when the mail receiving unit 11 receives an electronic mail transmitted from the user terminals 2 ₁ to 2 ₃ or an electronic mail transferred from another mail server, the electronic mail is stored in the mail storage unit 12 ( Step 71).

  Then, the transmission destination determination unit 63 determines the destination of the electronic mail stored in the mail storage unit 12, determines whether the destination of the electronic mail is local or remote, and when the destination is local The electronic mail is transferred to the local processing unit 64, and when the destination is remote, the electronic mail is transferred to the remote processing unit 15 (step 72). Then, the electronic mail transferred to the remote processing unit 15 is transferred to another server (step 73).

  The e-mail transferred to the local processing unit 64 first confirms whether or not the destination address actually exists locally (step 74). Is notified that no exists (step 75).

  If it is determined in step 74 that the destination address exists locally, it is checked whether or not the transmission source address corresponds to the reception rejection address stored in the blacklist server 4 (step 76). . If it is determined in step 76 that the transmission source address corresponds to the reception rejection address, a process set by the user such as discarding the e-mail is executed (step 77), and the process ends.

If it is determined in step 76 that the transmission source address does not correspond to the reception refusal address, after virus checking or the like is performed (step 78), the electronic mail is stored in the mailbox 16 of each user (step 78). 79). Then, the user can receive the e-mail by reading out the e-mail stored in the mail box 16 by each of the user terminals 2 ₁ to 2 ₃ .

  According to such a conventional e-mail transfer system, if the user registers in advance with the blacklist server 4 the address of the sender that does not want to receive the e-mail, the user will not receive spam mail from that sender. That's okay. However, according to this method, it is necessary for the user to set all addresses to be rejected to the blacklist server 4, which is troublesome. In addition, since it is not possible to set a reception rejection address in the blacklist server 4 without receiving at least one junk mail from one transmission source, it is not possible to deal with unknown addresses. Therefore, when spam mails from various senders are sent one after another, the reception of the spam mails cannot be effectively rejected.

  On the other hand, there may be a method in which an address that the user may receive is set in advance so that all e-mails transmitted from addresses other than the address designated by the user are not delivered to the user. . However, this method has a problem that even if the user does not specify all the addresses necessary for the user, even the necessary electronic mail is not distributed. In addition, the designated address must be constantly updated, which requires troublesome work.

The conventional electronic mail transfer system described above has the following problems.
(1) If delivery of an e-mail address specified by the user is not performed, the user must constantly update the address to be rejected, which requires troublesome work for the user and is unknown. Unable to respond to junk mail with your address.
(2) When an address that the user may receive is registered in advance and electronic mail other than that address is not distributed to the user terminal, the user specifies all addresses of the transmission source to be received in advance. If you do not register, you will not be able to receive the necessary emails.

  An object of the present invention is to provide a mail in an electronic mail transfer system that can effectively eliminate junk mail without requiring troublesome work for the user and without causing a situation where necessary mail cannot be received. Is to provide a server.

  In order to achieve the above object, the mail server according to the present invention causes the e-mail to be annoying when the number of local user addresses to which a certain e-mail is addressed is equal to or greater than a predetermined threshold value. Junk mail determination means for determining mail is included.

  Further, another mail server of the present invention has a predetermined number of e-mails that are the same as that of the stored e-mails and at least one of the transmission source, title, and data size is preset. When it is equal to or greater than the threshold value, the electronic mail has a junk mail determination unit that determines that the e-mail is a junk mail.

  Furthermore, when the number of local user addresses that are the destinations of a certain e-mail is equal to or greater than a predetermined first threshold value, the other e-mail server of the present invention is a junk e-mail. A first junk e-mail judging means for judging that the number of e-mails is the same as that of the stored e-mail and at least one of the sender, the title, and the data size is constant. If it is equal to or greater than the second threshold value, the electronic mail has second spam mail determination means for determining that the email is spam.

  According to the present invention, it is possible to prevent junk mail from being transferred even when the user does not bother with pre-registering the address of the sender from which he / she intends to refuse receipt.

As described above, according to the present invention, the following effects can be obtained.
(1) Spam mail delivery can be eliminated even if the user has not made any settings.
(2) Since the confirmation mail does not deliver the entire spam mail, the amount of packets can be reduced.
(3) Even when the mail server determines that the mail is spam, the user is always confirmed to receive the mail, so that no adverse effect such as discarding a necessary e-mail without the user's intention occurs. .

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an electronic mail transfer system according to an embodiment of the present invention. In FIG. 1, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 1, the electronic mail transfer system according to the present embodiment includes a mail server 10 ₁ to 10 _n functioning as an MTA, a DNS server 3, a user terminal 1, and a black connected to the mail server 10 _n. It comprises a list server 4, a determination unnecessary list server 5, and user terminals 2 ₁ to 2 ₃ .

  The determination-unnecessary list server 5 is for registering in advance the address of the sender that the user considers unnecessary to determine whether or not the message is spam. Accordingly, the e-mail from the address registered in the determination unnecessary list server 5 is not determined to be a junk mail.

As shown in FIG. 2, the mail server 10 _n includes a mail receiving unit 11, a mail storage unit 12, a transmission destination determination unit 13, a local processing unit 14, a remote processing unit 15, and a mailbox 16. The mail server 20 _n in the conventional electronic mail delivery system shown in FIG. 6 is replaced with the transmission destination determination unit 63 by the transmission destination determination unit 13 and the local processing unit 64 is replaced with the local processing unit 14. The only difference is that it has been replaced by.

Note that the mail server 10 _n may be configured not only by a single computer or the like but also by a plurality of computers or peripheral devices.

  The transmission destination determination unit 13 performs the same operation as the conventional transmission destination determination unit 63 shown in FIG. 6 except that the junk mail determination unit 17 is provided.

  The junk mail determination unit 17 determines that an e-mail that satisfies a certain condition among e-mails determined to be local by the transmission destination determination unit 13 is a junk mail.

  Here, as a predetermined condition that the junk mail determination unit 17 determines to be a junk mail, the number of local user addresses that are destinations of a certain e-mail and the mail storage unit 12 are stored. It is conceivable that the total number of e-mails in which at least one of the e-mails and the transmission source, title, and data size is equal to or greater than a predetermined threshold value.

  The local processing unit 14 performs the same operation as the conventional local processing unit 64 shown in FIG. 6 except that the junk mail processing unit 18 is provided.

  The local processing unit 14 transmits to the mailbox 16 as usual the ones that are determined not to be junk mail from the e-mails transmitted from the destination determination unit 13 and are determined to be junk mails as usual. Is processed in the junk mail processing unit 18.

  The junk mail processing unit 18, among the e-mails determined to be junk mail by the junk mail determination unit 17, for those whose sender address is registered in the determination unnecessary list server 5, It is determined that it is not a spam mail and is sent to the mail box 16 in the same manner as a normal electronic mail. Further, the spam mail processing unit 18 informs the user about an email whose sender address is not registered in the determination-unnecessary list server 5 among the emails determined to be spam by the spam mail determination unit 17. A confirmation mail for confirming whether or not to receive the junk mail is transmitted, and only a reply mail that is received from the user is transmitted to the mailbox 16.

  Next, the operation of the electronic mail delivery system of this embodiment will be described in detail with reference to the drawings.

  The operation of the electronic mail delivery system of this embodiment is shown in the flowchart of FIG.

  3 is different from the flowchart showing the operation of the conventional e-mail transfer system shown in FIG. 7 in that steps 31 to 34, which are processes by the junk mail determination unit 17, are performed between steps 72 and 74. In addition, Steps 35 to 38 which are processes by the junk mail processing unit 18 are added between Step 76 and Step 78. Therefore, in the following, only the processing added to FIG. 7 will be described, and description of other processing will be omitted.

  First, steps 31 to 34 which are processes by the junk mail determination unit 17 will be described.

The spam mail determination unit 17 counts the number of addresses of the local user terminals 2 ₁ to 2 ₃ included in the electronic mail whose destination is determined to be local in step 72, and sets the number as A ( Step 31).

  Here, the number of addresses included in the e-mail includes not only addresses described in “To” but also all addresses described in the “CC” column. That is, the number of addresses described in the envelope of the electronic mail is counted.

  Next, the junk e-mail determination unit 17 determines the number of e-mails stored in the e-mail storage unit 12 with the same e-mail and any of the transmission source, title, data size, and the like. Count and set the number to B (step 32).

  Then, it is determined whether or not the value of A + B obtained by adding A calculated in step 31 and B calculated in step 32 is equal to or larger than a predetermined threshold value (step 33). In step S34, the electronic mail is determined to be spam mail.

  The junk mail determination unit 17 determines whether or not an e-mail that is determined based on the total value of A + B is a junk mail. This is because there are ones that include an address and ones that replace an e-mail with a certain content and send it to many destinations. In other words, if the determination is made using only the value of A, it is not possible to detect junk mail whose destination contains only one mail address, and the determination is made using only the value of B. This is because it is not possible to detect spam mails in which many mail addresses are listed in the “To” and “CC” columns of one electronic mail.

  For example, as an example of the above threshold value, 120 e-mails per second, that is, 7000 e-mails per minute can be delivered, or a single e-mail can be sent on SMTP (Simple Mail Transfer Protocol). Considering that the upper limit of e-mails that can be written, that is, the upper limit of addresses that can be described in the envelope is 100, if the sum of A + B exceeds 50 in 10 seconds, the e-mail is determined to be spam.

  Moreover, you may use the value which multiplied the fixed ratio with respect to the user terminal connected to the mail server as a threshold value whether it is a spam mail. For example, when the number of user terminals is 500, 10% of 50 may be used as the threshold value.

  Next, steps 35 to 38 which are processes by the junk mail processing unit 18 will be described.

  The spam mail processing unit 18 first checks whether or not the email from the destination determination unit 13 is determined to be spam by the spam mail determination unit 17 (step 35), and determines that it is spam. If not, processing similar to that for normal e-mail is performed.

  If it is confirmed in step 35 that the e-mail is determined to be junk mail, the junk e-mail processing unit 18 determines whether or not the address of the e-mail transmission source is registered in the determination-unnecessary server 5. Is confirmed (step 36). When the sender address of the e-mail is registered in the determination-unnecessary server 5, the junk e-mail processing unit 18 performs the same process as the normal e-mail on the e-mail. If the sender address of the e-mail is not registered in the determination-unnecessary server 5, the junk mail processing unit 18 inquires of the user whether or not the junk mail is desired to be delivered (step 37). The electronic mail is delivered only when a reply is received from the user that the delivery is desired, and the electronic mail is discarded when a reply to the reception is rejected (step 38).

  Further, a specific example of the process of step 37 in the flowchart of FIG. 3 for confirming receipt of spam mail to the user will be described with reference to the flowchart of FIG.

First, the junk mail processing unit 18 sends a confirmation mail including any one of information such as a destination, a subject, a transmission source, and a part of contents of an electronic mail determined to be junk mail to the mailbox 16. Transmit (step 51). The user receives the confirmation mail from the mail box 16 via the user terminals 2 _{1 to} 2 ₃ (step 52), and determines whether or not to receive the electronic mail (step 53).

  If the user decides to receive the electronic mail, the user sends a reply to the confirmation mail to mail address # 1 (step 55). Then, the junk mail processing unit 18 confirms the returned mail address (step 56), and if it is confirmed that the mail address # 1, the electronic mail is subjected to a virus check or the like (step 78). The message is transmitted to the personal mailbox 16 (step 79).

  If the user decides in step 53 to refuse to receive the e-mail, a reply to the confirmation mail is sent to mail address # 2 (step 54). Then, the spam mail processing unit 18 confirms the returned mail address (step 56), and when confirming that the mail address is # 2, discards the electronic mail (step 38).

  In this description, when the user receives an e-mail that is determined to be junk mail, the user transmits a reply mail to the mail address # 1, and when rejecting the reception, the user sets the mail address # 2. Although the case where a reply mail is transmitted has been described, reception may be confirmed using other methods.

  For example, a specific address in the confirmation mail may be described, and the user may access the web page of the address and display an intention to determine whether or not to receive the address. Further, in the case of Webmail such as Hotmail, it may be displayed whether it is spam or not, and it may be determined whether or not it is received when the user accesses and retrieves the email. Furthermore, receipt may be confirmed on the mail using HTML mail. Further, if the user does not reply that he / she will receive the e-mail within a certain time after receiving the confirmation e-mail, the e-mail may be automatically deleted. In this way, if the user does not receive the mail, there is no need to bother sending a reply mail.

According to the e-mail transfer system of the present embodiment, it is possible to prevent junk e-mail from being transferred even when the user does not bother registering in advance the address of the sender from which he / she intends to refuse the receipt. Can do. Further, even if the spam has been transferred to the mail server 10 _n, to the mail server 10 each from _n user terminals 2 ₁ to 2 _3, the confirmation email overall only spam sent is forwarded Therefore, the amount of packets to the user can be reduced. Further, even if it is determined that the mail server 10 _n is a junk mail, the junk mail is not discarded immediately, but the receipt confirmation to the user is performed. Therefore, the necessary e-mail is discarded without the user's intention. No negative effects such as end.

  In general, an e-mail from a mailing list is often sent to a large number of destinations by one e-mail. Therefore, according to the e-mail transfer system of the present embodiment, there is a possibility that the e-mail is determined to be spam. is there. However, even in such a case, by registering the sender address of the mailing list registered by the user in the determination unnecessary list server 5, the user can be prevented from being erroneously determined as spam mail. it can.

  In the above description, the spam mail determination unit 17 has been described as performing the determination based on the total value of A + B. However, the first and second threshold values are set in advance, and the value of A is the first value. If the value is equal to or greater than the threshold value or the value of B is equal to or greater than the second threshold value, the electronic mail may be recognized as spam mail. Further, the spam mail determination unit 17 may determine whether the mail is spam based only on the value A or the value B.

In the present embodiment, the case where the present invention is applied only to the mail server 10 _n has been described for the sake of simplicity, but the present invention is also applied to the other mail servers 10 ₁ to 10 _n−1 . Can be similarly applied.

  Also, in the present embodiment, a case where a confirmation mail that is an e-mail is used as a method for confirming whether or not the junk mail processing unit 18 receives an e-mail that has been determined to be junk mail to the user will be described. However, the present invention is not limited to such a form. That is, as long as the junk mail processing unit 18 can confirm whether or not the user receives junk mail, the junk mail processing unit 18 is not limited to an e-mail form such as a confirmation mail. Any form may be used as long as 18 is a confirmation message that can convey some information to the user.

  Furthermore, in the present embodiment, the junk mail processing unit 18 confirms the user whether or not the junk mail determination unit 17 determines that the junk mail is junk mail after receiving the junk mail. When transmission to the mail box 16 is performed, but the spam mail determination unit 17 determines that the email is spam, the user terminal determines that the email is spam. Only the message may be transmitted. Specifically, when it is determined by the junk mail determination unit 17 that a certain e-mail is junk mail, it is determined that the e-mail is junk mail without confirming the user's will. A form in which the message is attached and immediately sent to the mailbox 16 is conceivable.

Furthermore, in this embodiment, the list of addresses of the sender that the user refuses to receive and the list of addresses of the sender that the user thinks is not necessary to determine whether or not the junk mail is not included in the black list server 4, Although the description has been given using the case where the information is stored in an independent server called the determination unnecessary list server 5, the present invention is not limited to such a form. For example, the present invention can be similarly applied to a form in which such a list of sender addresses is stored in the mail server 10 _n .

  Further, although not shown in FIG. 1, the mail server in the electronic mail transfer system of the present embodiment may be provided with a recording medium on which a program for executing the electronic mail transfer system method is recorded. This recording medium may be a magnetic disk, a semiconductor memory, or another recording medium. Then, this program is read from the recording medium into the mail server and controls the operation of the mail server, and the mail server executes the above processing under the control of this program.

It is a block diagram which shows the structure of the electronic mail transfer system of one Embodiment of this invention. It is a block diagram which shows the structure of the mail server 10 _n in FIG. It is a flowchart which shows operation | movement of the electronic mail transfer system of one Embodiment of this invention. It is a flowchart which shows the specific example of step 37 which performs reception confirmation in FIG. It is a block diagram which shows the structure of the conventional electronic mail transfer system. It is a block diagram which shows the structure of the mail server 20 _n in FIG. It is a flowchart which shows operation | movement of the conventional electronic mail transfer system.

Explanation of symbols

1 user terminal 2 ₁ , 2 ₂ , 2 ₃ user terminal 4 black list server 5 determination unnecessary list server 10 ₁ to 10 _n mail server 11 mail receiving unit 12 mail storage unit 13 destination determination unit 14 local processing unit 15 remote processing unit 16 mailbox 17 spam classification unit 18 junk mail processing unit 20 ₁ to 20 _n mail server 31 through 38 steps 51-56 step 63 destination determining unit 64 local processing unit 71 to 79 step

Claims (3)

  A mail server having a junk mail determination unit that determines that an e-mail is a junk mail when the number of local user addresses that are the destination of the e-mail is equal to or greater than a predetermined threshold value.   If the number of emails in which at least one of the stored emails is the same as the sender, title, and data size is equal to or greater than a predetermined threshold value, the email is A mail server having a spam mail judging means for judging that it is a spam mail.   First junk e-mail determination that determines that an e-mail is junk mail when the number of local user addresses that are the destination of the e-mail is equal to or greater than a predetermined first threshold value Means or when the number of e-mails in which at least one of the stored e-mail and the sender, title, and data size is equal to or larger than a predetermined second threshold value A mail server having second junk mail judging means for judging that the electronic mail is junk mail.

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