JP2016072809A - Program and mail server - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a program capable of reducing processing load of a mail server and shortening processing time of delivery of e-mail by using a technique of connection pool in the mail server, and to provide the mail server.SOLUTION: When a domain of a destination of newly received e-mail is stored in a storage part, processing of delivering the e-mail is performed by using connection with a connection destination address corresponding to the domain of the destination of the e-mail.SELECTED DRAWING: Figure 6A

Description

  The present invention relates to a program and a mail server.

  2. Description of the Related Art Conventionally, there is a mail server that receives and delivers an electronic mail on a network through SMTP (Simple Mail Transfer Protocol) (for example, Patent Document 1).

  Conventionally, there is a technique called a connection pool in order to reduce the communication load and shorten the time required for access. The connection pool is also called connection pooling, and refers to communication processing that uses a connection established in advance, instead of establishing a connection (connection) for each access.

  For example, Patent Document 2 discloses a database system in which a plurality of connections are prepared in advance between an application and a database server, and a pooled connection is used when a connection acquisition request is issued from the application ( (See FIG. 4 of Patent Document 2).

JP 2012-029009 A JP 2007-226398 A

  The mail server makes an inquiry to a DNS server (DNS is an abbreviation of “Domain Name System”, hereinafter the same) based on the destination domain, and the IP address of the connection destination (delivery destination) (IP is “Internet protocol ( (Internet Protocol) ", hereinafter the same) is acquired, and a communication path for communicating with the mail server of the IP address is established to deliver the e-mail.

  In the conventional mail server, there was no idea of a connection pool for reusing connections. Therefore, for example, even when delivering multiple e-mails addressed to the same domain, each time an e-mail is delivered, the connection destination IP address is acquired and the connection is established and delivered, and the delivery ends. Then, since the process of disconnecting is performed, it takes time to establish and disconnect the communication path.

  In recent years when communication by e-mail has been increasing more and more, it has become a problem to reduce the processing load of the mail server and shorten the processing time.

  The present invention has been made in view of the above-described problems, and its purpose is to use connection pool technology in a mail server, to reduce the processing load on the mail server, and to shorten the processing time for delivery of email. Providing a simple program and a mail server.

(1) The present invention
A program for a mail server that delivers electronic mail,
An accepting unit for processing to accept an e-mail;
A delivery unit that obtains a connection destination address from a DNS server based on the domain of the destination of the email, connects to the obtained connection destination address, and delivers the email;
A connection pool section that holds a connection to the connection destination address;
When the connection to the connection destination address is held, the computer is caused to function as a connection information management unit that performs processing for associating and storing the domain of the destination of the e-mail and the connection destination address in the storage unit. ,
The delivery unit is
When the newly accepted domain of the email destination is stored in the storage unit, a process of delivering the email using the connection of the connection destination address corresponding to the domain of the email destination Regarding the program.

  The present invention also relates to an information storage medium storing the program and a mail server configured as each unit.

  Here, the connection destination address is an address on the network of the mail server of the delivery destination for delivering the e-mail. For example, in order to identify a device on the network with an IP address (IP such as IPv4 or IPv6) (Identification number in the specified network layer).

  According to the present invention, when a domain of a newly received e-mail destination is stored in the storage unit, the e-mail is transmitted using a connection of a connection destination address corresponding to the e-mail destination domain. The process of acquiring a new e-mail connection destination address and the process of establishing a connection can be omitted, reducing the processing load on the mail server and reducing the e-mail delivery processing time. It can be shortened.

(2) Also, the program, information storage medium and mail server of the present invention are:
The connection information management unit
Processing for storing the domain of the e-mail destination, the host, and the connection destination address as a set in the storage unit when the host of the MX record can be obtained from the DNS server based on the domain of the e-mail destination And
When the MX record host cannot be obtained from the DNS server based on the domain of the email destination, the domain of the email destination is the host, the host and the connection destination address are associated with each other in the storage unit. Process to remember,
The delivery unit is
Deliver the e-mail using the connection of the connection destination address corresponding to the destination domain of the e-mail when the newly accepted e-mail destination domain is stored as a domain or host in the storage unit You may perform the process to do.

  According to the present invention, when a newly accepted domain of an email is stored as a domain or a host in the storage unit, the connection of the connection destination address corresponding to the domain of the email destination is used. The process of delivering the e-mail is performed so that the process of acquiring the mail server host of the new e-mail destination domain, the process of acquiring the connection destination address, and the process of establishing the connection can be omitted. It is possible to reduce the processing load on the server and shorten the processing time for delivery of e-mail.

  The set of “e-mail destination domain, host, connection destination address” stored in the storage unit has a correspondence relationship between the e-mail destination domain and the host. There is a correspondence relationship between the domain of the destination of the e-mail and the connection destination address.

(3) The program, information storage medium and mail server of the present invention are:
The connection information management unit
Processing for storing the domain of the e-mail destination, the host, and the connection destination address as a set in the storage unit when the host of the MX record can be obtained from the DNS server based on the domain of the e-mail destination And
When the MX record host cannot be obtained from the DNS server based on the domain of the email destination, the domain of the email destination is the host, the host and the connection destination address are associated with each other in the storage unit. Process to remember,
The delivery unit is
If the newly accepted email destination domain is not stored as a domain or host in the storage unit, the MX record host is acquired by the DNS server based on the newly accepted email destination domain. When the request is made and the host is acquired, the electronic mail is delivered using the connection of the connection destination address corresponding to the host when the host is stored as the host in the storage unit. Processing may be performed.

  According to the present invention, when the domain of the newly received e-mail destination is not stored as a domain or host in the storage unit, the e-mail destination domain is newly set in the DNS server based on the newly received e-mail destination domain. If the host of MX record is requested and the host can be acquired, if the host is stored as a host in the storage unit, the connection of the connection destination address corresponding to the host is used. Since the process of delivering the e-mail is performed, it is possible to omit the process of acquiring a new e-mail connection destination address and the process of establishing a connection, reducing the processing load on the mail server, and e-mail delivery. Processing time can be shortened.

(4) Further, the program, information storage medium and mail server of the present invention are:
The delivery unit is
When multiple emails addressed to the same domain are accepted, multiple connections are established for the domain under the specified conditions, and multiple emails are delivered in parallel.
The connection pool section
Keep multiple connections,
The connection information management unit
For each connection, perform a process of associating the destination domain of the e-mail with a connection destination address and storing it in the storage unit,
The delivery unit is
When a plurality of connection destination addresses for the destination domain of the newly received e-mail are stored in the storage unit, the process of delivering the e-mail using the connection of any connection destination address that is not being delivered May be performed.

  According to the present invention, when a plurality of e-mails having the same destination domain are received, a plurality of connections are established to the domain under a predetermined condition, and a process of delivering a plurality of e-mails in parallel is performed. That is, according to the present invention, it is possible to increase the number of connection pools for the domain under a predetermined condition. For example, when a large number of emails with the same destination domain are received, the destination of the email Since the process of delivering the e-mail using a connection that is not being delivered (free) of the connection address corresponding to the domain is performed, the host acquisition process and the connection destination of the mail server of the new e-mail destination domain It is possible to distribute delivery processing while omitting address acquisition processing and connection establishment processing, reducing the processing load of the mail server and shortening the processing time of electronic mail delivery.

(5) Further, the program, the information storage medium and the mail server of the present invention are:
The connection pool section
If the domain of the e-mail destination is a specific domain, hold the connection to the connection destination address based on the domain,
When the domain of the destination of the electronic mail is not a specific domain, after the electronic mail is delivered, the connection to the connection destination address based on the domain may be disconnected.

  According to the present invention, since the connection is held for the specific domain, the delivery process can be performed efficiently. For example, when it is expected that the number of electronic mails destined for a specific domain will be large, it is possible to efficiently deliver electronic mails destined for a specific domain by utilizing the connection pool to reduce the processing load. Further, since the connection pool is not used for e-mails destined for a destination other than the specific domain, it is possible to avoid wasting system resources.

(6) Further, the program, information storage medium and mail server of the present invention are:
The connection information management unit
A process of storing the domain of the destination of the email, the connection destination address, and a connection status indicating whether or not the connection is held in the storage unit as a set;
The delivery unit is
When the newly accepted domain of the destination of the email is stored in the storage unit, and the connection status corresponding to the domain of the destination of the email is information indicating that the connection is held Performs the process of delivering the email using the connection of the connection destination address corresponding to the domain of the destination of the email,
When the newly accepted domain of the destination of the email is stored in the storage unit, and the connection status corresponding to the domain of the destination of the email is information indicating that the connection is not held Performs a process of connecting to the connection destination address corresponding to the domain of the destination of the email and delivering the email,
The connection information management unit
When the connection to the connection destination address is held, the connection status corresponding to the domain of the e-mail destination is set to information indicating that the connection is held,
When the connection to the connection destination address is not held, the connection status corresponding to the domain of the e-mail destination may be set to information indicating that the connection is not held.

  According to the present invention, even if the connection to the connection destination address corresponding to the domain of the destination of the newly accepted e-mail is not held, the DNS server is stored when the domain is stored in the storage unit. It is possible to omit the process of acquiring the connection destination address and establish the connection to the connection destination address and deliver the e-mail. In addition, according to the present invention, when the connection to the connection destination address corresponding to the domain of the destination of the newly accepted electronic mail is held, the connection destination address acquisition process to the DNS server, and the connection E-mail can be delivered by omitting the process of establishing. Therefore, according to the present invention, it is possible to further reduce the processing load of the mail server and shorten the processing time for the delivery of electronic mail.

  The set of “email destination domain, connection destination address, and connection status” stored in the storage unit has a correspondence relationship between the email destination domain and the connection destination address. The connection status has a correspondence relationship, and the domain of the e-mail destination and the connection status have a correspondence relationship.

(7) Further, the program, information storage medium and mail server of the present invention are:
The delivery unit is
Processing of delivering the e-mail using the connection of the connection destination address when the connection destination address acquired from the DNS server based on the newly received domain of the e-mail is stored in the storage unit May be performed.

  According to the present invention, when the connection destination address acquired from the DNS server based on the newly received domain of the e-mail is stored in the storage unit, the connection using the connection destination address is used to Since the process for delivering the e-mail is performed, the process for establishing the connection can be omitted, the processing load on the mail server can be reduced, and the e-mail delivery processing time can be shortened.

An example of the network diagram of this embodiment. An example of a functional block diagram of the mail server of this embodiment. Explanatory drawing of the method of acquiring the connecting address of this embodiment. Explanatory drawing of the connection information of this embodiment. Explanatory drawing of the connection information of this embodiment. The flowchart figure of the process of this embodiment. The flowchart figure of the process of this embodiment. The flowchart figure of the process of this embodiment. The flowchart figure of the process of this embodiment. The flowchart figure of the process of this embodiment. The flowchart figure of the process of this embodiment.

  Hereinafter, this embodiment will be described. In addition, this embodiment demonstrated below does not unduly limit the content of this invention described in the claim. In addition, all the configurations described in the present embodiment are not necessarily essential configuration requirements of the present invention.

1. Network FIG. 1 is an example of a network diagram of the present embodiment. The mail server 10 of this embodiment is an MTA (Mail Transfer Agent) that accepts (receives) and delivers electronic mail over a network via SMTP.

  The mail server 10 receives an email including an envelope destination (destination email address), an envelope sender (sender email address), and a message used for delivery processing, and receives the email received via the network. Based on the envelope destination, processing is performed for delivery to a delivery destination mail server (transmission destination mail server).

  More specifically, the mail server 10 accepts an e-mail transmitted from a MUA (Mail User Agent). Note that MUA is a client program used to send and receive e-mails at terminals on the Internet.

  Next, the mail server 10 sends the received e-mail to the DNS server that manages the destination domain of the envelope of the received e-mail, the DNS server in the local area of the mail server 10, or another DNS server. Queries the host of the MX record of the envelope destination domain. For example, the mail server 10 inquires the MX record of the destination domain from the DNS server, and acquires the domain host.

When the mail server 10 can acquire the host of the MX record of the destination domain of the envelope of the received electronic mail, the mail server 10 inquires about the IP address of the host. Further, when the mail server cannot acquire the host of the MX record of the domain of the destination of the envelope of the received electronic mail, it inquires about the IP address by designating the domain as the host. For example, the mail server 10 queries the DNS server for the A record of the host (in the case of IPv6, the AAAA record, the same applies hereinafter), and acquires the IP address of the host. That is, this IP address becomes the delivery address of the delivery mail server.

  Then, the mail server 10 establishes a connection with the delivery destination mail server based on the IP address, and performs processing for delivering (delivery, transmission, transfer, relay) of the electronic mail.

  The mail server 10 according to the present embodiment accepts an e-mail includes a case where an e-mail is accepted from a terminal via SMTP and a case where an e-mail delivered from another mail server is accepted via SMTP.

  Also, the mail server 10 of the present embodiment delivers an e-mail to a process of delivering a received e-mail to another mail server via SMTP, or to a user who has an account in the same system where the mail server 10 operates. Processing for delivering to a local delivery agent MDA (Mail Delivery Agent) for delivery to the user, and processing for delivering locally to a user who has an account in the same system where the mail server operates without going through MDA.

2. Configuration FIG. 2 is an example of a functional block diagram of the mail server 10 of the present embodiment. Note that the mail server 10 according to the present embodiment does not need to include all the units illustrated in FIG. 2 and may have a configuration in which some of the units are omitted.

  The storage unit 170 serves as a work area for the processing unit 100 and the like, and its function can be realized by hardware such as RAM (VRAM).

  The storage unit 170 of this embodiment includes connection information 171. The connection information 171 is pooled connection information and includes a domain, a host, and a connection destination address (IP address). The domain, host, and connection destination address are stored as a set. In a set of domains, hosts, and connection destination addresses, the domain and the host have a correspondence relationship, the host and the connection destination address have a correspondence relationship, and the domain and the connection destination address have a correspondence relationship. The same applies to the following description.

  Further, the connection information 171 may include a connection status indicating whether or not the connection is held. When the connection status is included, the connection status is stored as a set with the domain, the host, and the connection destination address. The same applies to the following description.

  In the storage unit 170, a spool area (storage area) for temporarily storing the e-mail received by the receiving unit 111 may be secured. Note that the e-mail stored in the spool area is deleted from the spool area when the delivery process is completed (normal delivery end or delivery error end). In the case of a delivery error end, that is, an electronic mail that cannot be delivered to the delivery destination mail server is stored again in the spool area.

The information storage medium 180 can be read by a computer, and the information storage medium 180 stores programs, data, and the like. That is, the information storage medium 180 stores a program for causing a computer to function as each unit of the present embodiment (a program for causing a computer to execute processing of each unit). That is, the processing unit 100 can perform various processes of the present embodiment based on data read from a program (data) stored in the information storage medium 180.

  For example, the information storage medium 180 is an optical disk (CD, DVD), a magneto-optical disk (MO), a magnetic disk, a hard disk, a magnetic tape, a memory (ROM), a memory card, or the like.

  The processing unit 100 performs various processes of the present embodiment based on a program (data) stored in the storage unit 170. Note that the processing unit 100 of the present embodiment reads the program and data stored in the information storage medium 180, stores the read program and data in the storage unit 170, and performs processing based on the program and data. Also good.

  The processing unit 100 (processor) performs various processes using the main storage unit in the storage unit 170 as a work area. The functions of the processing unit 100 can be realized by hardware such as various processors (CPU, DSP, etc.) and programs.

  The processing unit 100 includes a receiving unit 111, a connection pool unit 112, a connection information management unit 114, and a delivery unit 115.

  The accepting unit 111 performs a process of accepting (receiving) an e-mail that is transmitted from the sender and designated as an envelope destination by the MUA of the terminal (computer, mobile phone, tablet computer, smartphone).

  The connection pool unit 112 performs processing for holding (maintaining) the connection to the connection destination address connected when the electronic mail is delivered. For example, the connection to the connection destination address is maintained for a predetermined period (until a timeout occurs), and is disconnected after the predetermined period has elapsed.

  Further, the connection pool unit 112 may hold a plurality of connections. For example, connections to the same or different connection destination addresses may be held.

  In addition, when the domain of the email destination is a specific domain, the connection pool unit 112 holds the connection to the connection destination address based on the domain, and when the domain of the email destination is not the specific domain After the electronic mail is delivered, the connection to the connection destination address based on the domain may be disconnected.

  The connection information management unit 114 stores the connection destination address and the connection destination address of the e-mail as a set as connection information when holding the connection to the connection destination address connected when the e-mail is delivered. A process of storing (registering) in the unit is performed.

  For example, when the connection information management unit 114 can acquire the MX record host of the domain of the e-mail destination from the DNS server, the domain of the e-mail destination, the host, and the connection destination address are set as one set. Processing to store in the storage unit as connection information is performed.

  In addition, when the connection information management unit 114 cannot obtain the host of the MX record of the domain of the destination of the email from the DNS server, the domain of the destination email address of the email is set as the host, and the host and the connection destination address are set. A set of connection information is stored in the storage unit.

In addition, when a plurality of connections are held, the connection information management unit 114 performs a process of storing an email destination domain and a connection destination address in association with each other for each connection.

  In addition, the connection information management unit 114 indicates whether or not the connection destination address, the connection destination address, and whether or not the connection is held regardless of whether or not the connection to the connection destination address is held. You may perform the process which memorize | stores a status in a memory | storage part as one set. Then, when the connection information management unit 114 holds the connection to the connection destination address, the connection information management unit 114 sets the connection status corresponding to the domain of the destination of the e-mail to information indicating that the connection is held, When the connection to the connection destination address is not held, the connection status corresponding to the domain of the e-mail destination is set to information indicating that the connection is not held.

  The delivery unit 115 performs a process of delivering the accepted electronic mail. For example, the delivery unit 115 acquires a connection destination address (for example, the IP address of the connection destination mail server) from the DNS server based on the domain of the destination mail address of the email, and connects to the connection destination address to send the email. Process to deliver.

  Further, when a new e-mail is received, the delivery unit 115 determines whether the destination domain of the e-mail is stored in the storage unit (determines whether it is stored as connection information). . When the domain of the destination of the e-mail is stored in the storage unit (when stored as connection information), the connection of the connection destination address corresponding to the domain of the destination of the e-mail is used. Processing to deliver the electronic mail is performed.

  For example, when a new e-mail is received, the delivery unit 115 determines whether the destination domain of the e-mail is stored as a domain or host in the storage unit (stored as a domain or host of connection information). To determine whether or not Then, when the domain of the destination of the email is stored as a domain or host in the storage unit (when stored as the domain or host of the connection information), the connection destination corresponding to the domain of the destination of the email A process of delivering the e-mail using the address connection is performed.

  Further, for example, when the newly accepted email destination domain is not stored as a domain or host in the storage unit, the delivery unit 115 performs DNS based on the newly accepted email destination domain. If the host of the MX record is requested to be acquired from the server and the host can be acquired, the host is stored in the storage unit as a host (when stored as the connection information host). A process of delivering the e-mail using the connection of the connection destination address corresponding to the host is performed.

  In addition, when receiving a plurality of e-mails having the same destination domain, the delivery unit 115 performs a process of establishing a plurality of connections to the domain under a predetermined condition and delivering a plurality of e-mails in parallel. May be. When the storage unit stores a plurality of connection destination addresses for the newly received email destination domain, the delivery unit 115 connects to any connection destination address that is not being delivered (free). The process of delivering the e-mail using is performed.

In addition, the delivery unit 115 is a case where the newly received email destination domain is stored in the storage unit, and the connection status corresponding to the email destination domain holds the connection. In the case of information indicating the destination, a process of delivering the e-mail using the connection of the connection destination address corresponding to the destination domain of the e-mail is performed, and the newly accepted e-mail destination domain is stored in the storage unit. If the connection status corresponding to the domain of the email destination is information indicating that the connection is not held, the connection destination corresponding to the domain of the email destination A process of delivering an email by connecting to an address may be performed.

  Further, when the connection destination address acquired from the DNS server based on the newly received domain of the email is stored in the storage unit, the delivery unit 115 uses the connection of the connection destination address to Processing for delivering electronic mail may be performed.

3. Description of processing of this embodiment (1) Outline of delivery The mail server of this embodiment accesses a DNS server when delivering an e-mail, and based on the domain of the destination of the envelope of the e-mail, the MX record of the domain And obtain the host (mail server) of the connection destination (delivery destination). If the host can be acquired, the DNS server is inquired of the A record, and the IP address of the delivery destination host is acquired. The mail server establishes a connection (connection) to the acquired IP address by TCP (Transmission Control Protocol), and performs a process of delivering an electronic mail by SMTP.

  In particular, in the present embodiment, once a connection is established, the connection is maintained (maintained, pooled) until a predetermined period determined in advance by a mail server, and an e-mail addressed to the same domain is delivered using the connection. Process.

(2) Connection establishment First, the details when the mail server establishes a connection will be described. For example, when receiving an e-mail addressed to “aaa@xxx.co.jp” (envelope destination), the mail server extracts the domain “xxx.co.jp” and is described in the MX record. An acquisition request is made to the DNS server for the host of the domain “xxx.co.jp”. For example, as shown in FIG. 3, “mail1.xxx.co.jp”, “mail2.xxx.co.jp”, and “mail3.xxx.co.jp” are associated with the domain “xxx.co.jp”. Get the host. There may be one or more hosts to acquire.

  Then, the mail server selects one host arbitrarily or according to the priority, and further requests the DNS server to acquire the IP address of the host described in the A record. For example, when the IP address “211.125.95.188” of “mail1.xxx.co.jp” is acquired, the connection of the IP address is established to open the communication path. Then, after the connection is established, a process of delivering (sending) e-mail data destined for “aaa@xxx.co.jp” to the delivery destination mail server is performed.

  There may be a plurality of IP addresses for the host, and when there are a plurality of IP addresses, the IP address selected by the DNS server is received. When the mail server receives a plurality of IP addresses from the DNS server, the IP address of one connection destination is selected arbitrarily or according to the priority.

(3) Connection Pool In this embodiment, a connection pool technology is used for the mail server. In other words, the mail server according to the present embodiment omits the process of reusing and establishing a connection when a connection that currently holds the destination domain of the received electronic mail can be used. This is because the processing load on the mail server can be reduced and the processing time for delivery of electronic mail can be shortened.

  For example, as shown in FIG. 3, there may be a plurality of hosts in an email destination domain, and there may be a plurality of IP addresses for each host. And there are nine IP addresses for delivery of e-mail addressed to the domain “xxx.co.jp”, for example, A1 to A3, B1 to B3, C1 to C3, and can be delivered to any IP address. It is. Each time the mail server receives an e-mail addressed to the same domain, it acquires the host or IP address, establishes one of these nine connections, and performs a process of disconnecting after delivery, which is inefficient.

  Therefore, in this embodiment, the delivery of an e-mail addressed to the same domain uses the held connection, omits the acquisition of the host and IP address, and further omits the process of establishing the connection, It is controlled to reduce the processing load.

  For example, when an e-mail addressed to “aaa@xxx.co.jp” is delivered, the connection of the domain “xxx.co.jp” is maintained for a predetermined period (for example, 30 seconds) from the end of delivery, and the connection is established. In the case where an e-mail addressed to the same domain “xxx.co.jp” is newly accepted, for example, an e-mail addressed to “bbb@xxx.co.jp” is accepted, An e-mail addressed to “bbb@xxx.co.jp” is delivered using the held connection.

  Further, as shown in FIG. 4, the mail server of the present embodiment stores connection information CN1 in which the connection of the domain of the destination of the e-mail is held in the storage unit. The connection information CN1 includes a connected domain, host, and IP address, and stores the domain, host, and IP address as a set.

  In the present embodiment, the connection information CN1 related to the IP address is stored from when the connection of the IP address is started until the connection is terminated (disconnected), and the connection information CN1 is stored at the timing when the connection is completed. Process to delete from.

  The mail server determines whether there is a held connection by extracting the domain part of the e-mail destination and determining whether the extracted domain is stored as the domain of the connection information. .

  For example, when an e-mail addressed to “bbb@xxx.co.jp” is received, it is determined whether or not the domain “xxx.co.jp” is stored as connection information. For example, as shown in FIG. 4, when the domain “xxx.co.jp” is stored as the connection information CN1, the IP address “211.125.95.188” corresponding to “xxx.co.jp” is stored. ”Is used to deliver an e-mail addressed to“ bbb@xxx.co.jp ”.

(4) When E-mail Destination Domain is Host If the extracted e-mail destination domain is not stored as connection information, the mail server requests the DNS server to acquire the host of the MX record. In such a case, if the MX record host cannot be obtained from the DNS server, the connection is established by designating the domain as the host.

For example, when the mail server accepts an e-mail addressed to “ccc@mail2.xxx.co.jp”, the mail server extracts the domain of the address and MX record of the domain “mail2.xxx.co.jp” Is inquired of the DNS server. However, if there is no MX record of the domain “mail2.xxx.co.jp” and the host of the MX record of the domain cannot be acquired from the DNS server, “mail2.xxx.co.jp” is designated as the host. Then, the mail server obtains the IP address of the host “mail2.xxx.co.jp” by inquiring the DNS server for an A record. For example, “221.125.95.185” is acquired by inquiring the DNS server for an A record for the IP address of the host “mail2.xxx.co.jp”. Then, the mail server establishes a connection with the acquired IP address and performs processing for delivering an e-mail addressed to “ccc@mail2.xxx.co.jp”. Then, the connection of the host “mail2.xxx.co.jp” is held for a predetermined period from the end of delivery, and as shown in FIG. 5A, the host “mail2.xxx.co.jp” and the IP The address “211.125.95.185” is associated and stored in the storage unit as connection information CN2. If the host of the MX record of the destination domain “mail2.xxx.co.jp” cannot be acquired from the DNS server and “mail2.xxx.co.jp” is designated as the host, the domain of the connection information CN2 Is not set (not stored).

  For example, when an e-mail addressed to “ddd@mail2.xxx.co.jp” is received, is the destination domain “mail2.xxx.co.jp” stored as the domain or host of the connection information? Judge whether or not. For example, as shown in FIG. 5A, when “mail2.xxx.co.jp” is stored as the host of the connection information CN2, the IP corresponding to the host “mail2.xxx.co.jp” is stored. A process of delivering an e-mail addressed to “ddd@mail2.xxx.co.jp” is performed using the connection of the address “211.125.95.185”.

  Also, for example, when an e-mail addressed to “eee@xxx.co.jp” is received, it is determined whether or not the destination domain “xxx.co.jp” is stored as a domain or host of connection information. To do. For example, when the connection information currently stored in the storage unit is only the connection information CN2 as shown in FIG. 5A, the host “mail2.xxx.co.jp” is the destination domain “xxx”. .Co.jp "is not stored as the domain or host of the connection information. Therefore, the mail server requests the DNS server to acquire the host of the domain “xxx.co.jp” described in the MX record. For example, as shown in FIG. 3, “mail1.xxx.co.jp”, “mail2.xxx.co.jp”, and “mail3.xxx.co.jp” are associated with the domain “xxx.co.jp”. Acquire three hosts. Then, since the acquired host “mail2.xxx.co.jp” is stored as connection information, the electronic mail is delivered using the connection of the IP address of the connection information. In other words, when the current connection information is the host “mail2.xxx.co.jp” having only the connection information CN2 as shown in FIG. 5A, the host “mail2.xxx.co.jp” A process for delivering an e-mail addressed to “eee@xxx.co.jp” is performed using the connection of the IP address “211.125.95.185” corresponding to

  Further, in this way, the domain “xxx.co.jp” of the e-mail addressed to “eee@xxx.co.jp” has no domain information of the connection information CN2 already stored, and the host has connection information. As shown in FIG. 5B, the domain “xxx.co.jp” is overwritten and stored in the connection information CN2. This is because, for e-mail addressed to the domain “xxx.co.jp”, a request for acquiring the host of the MX record from the DNS server is no longer necessary, and the processing load can be reduced.

(5) Processing example in the case where the acquired IP address is stored In the present embodiment, when the domain of the destination of the newly accepted e-mail is not stored as the domain or host of the connection information in the storage unit, The host of the MX record is acquired from the DNS server based on the domain of the received e-mail destination. If the host of the MX record can be acquired from the DNS server, the IP address of the A record is acquired from the DNS server to the DNS server. Request acquisition. If the MX record host cannot be acquired from the DNS server, the newly received e-mail destination domain is set as the host, and an IP address of the A record is requested to be acquired from the DNS server based on the host.

  In the present embodiment, even when the destination domain of the newly accepted e-mail is not stored as a connection information domain or host in the storage unit, the acquired IP address is stored as connection information in the storage unit. May perform processing for delivering the electronic mail using the connection of the IP address. This is because the process of establishing a connection is omitted, and the processing load can be reduced.

  If the host of the MX record can be acquired from the DNS server, the IP address already stored as connection information, the domain of the newly received e-mail destination, the host of the MX record acquired from the DNS server are displayed. Remember as a set. Further, when the host of the MX record cannot be obtained from the DNS server and the newly accepted e-mail destination domain is the host, the IP address already stored as connection information, the host (the domain is not set) ) As a set.

(6) Flow of delivery process Next, the flow of the delivery process of this embodiment is demonstrated using FIG. 6A, FIG. 6B, FIG. 6C, FIG. 6D, and FIG. First, as shown in FIG. 6A, when an e-mail is accepted (step S1), a process of extracting a destination domain is performed (step S2). Then, it is determined whether or not the extracted domain is stored as the domain or host of the connection information (step S3).

  If the extracted domain is stored as a connection information domain or host (Y in step S3), an electronic connection is made using an IP address connection corresponding to the extracted domain (connection information domain or host). Processing for delivering mail is performed (step S4).

  On the other hand, when the extracted domain is not stored as the domain or host of the connection information (N in Step S3), as shown in FIG. 6B, the host of the MX record is acquired from the DNS server (Step S5). Then, it is determined whether or not one or more MX record hosts have been acquired from the DNS server (step S6). If one or more MX record hosts have been acquired from the DNS server (Y in step S6), step S8 is performed. If no host of the MX record has been acquired from the DNS server (N in step S6), a process using the extracted domain as a host is performed (step S7).

  Then, a loop 1 process is repeated in which the processes in steps S8 to S15 are repeated until all the hosts are checked.

  First, it is determined whether or not the host is stored as the connection information host (step S9).

If the host is stored as the host of connection information (Y in step S9), the process proceeds to step S20. Then, as shown in FIG. 6C, a process of delivering an e-mail using the connection of the IP address corresponding to the host (host of the connection information) is performed (step S20).

  Then, it is determined whether or not the extracted domain is a host (step S21). If the extracted domain is not a host (N in step S21), the extracted domain is set as the host and IP address of the connection information. Are stored in the storage unit (step S22). On the other hand, if the extracted domain is a host (Y in step S21), the process proceeds to step S23. Then, the loop (loop 1) is interrupted (step S23), and the process is terminated.

  On the other hand, as shown in FIG. 6B, when the host is not stored as the host of the connection information (N in step S9), the IP address of the A record of the host is acquired from the DNS server (step S10). Then, the process of loop 2 is repeated to repeat the processes of steps S11 to S14 until all acquired IP addresses are checked.

  First, it is determined whether or not the acquired IP address is stored as the IP address of the connection information (step S12). If the acquired IP address is stored as the IP address of the connection information (Y in step S12), the process proceeds to step S30. Then, as shown in FIG. 6D, processing for delivering an e-mail using the connection of the acquired IP address (IP address of connection information) is performed (step S30).

  Then, it is determined whether or not the extracted domain is a host (step S31). If the extracted domain is not a host (N in step S31), the extracted domain and the host are set as the IP of the connection information. A pair with the address is stored in the storage unit (step S32). On the other hand, when the extracted domain is a host (Y in step S31), only the host (domain is not set) is stored in the storage unit as a set with the IP address of the connection information (step S34). ). Then, the loop (loop 1 and loop 2) is interrupted (step S33), and the process is terminated.

  On the other hand, as shown in FIG. 6B, when the acquired IP address is not stored as the IP address of the connection information (N in step S12), it is determined whether or not the connection to the acquired IP address has been established (step S13). .

  If it is possible to connect to the acquired IP address (Y in step S13), the process proceeds to step S40. Then, as shown in FIG. 6E, a process for delivering an electronic mail is performed (step S40). Then, it is determined whether or not the extracted domain is a host (step S41). If the extracted domain is not a host (N in step S41), the extracted domain, the host, and the acquired IP address are As a set, processing for storing the connection information in the storage unit is performed (step S42). On the other hand, if the extracted domain is a host (Y in step S41), the host and the acquired IP address are stored in the storage unit as connection information as a set (step S44). Then, the loop (loop 1 and loop 2) is interrupted (step S43), and the process is terminated.

  On the other hand, as shown in FIG. 6B, when connection to the IP address is not possible (N in step S13), the process of loop 2 is performed for the acquired next IP address. If all the acquired IP addresses are checked, loop 2 is terminated and the process returns to loop 1. That is, the process of loop 1 is performed for the acquired next host. If all acquired hosts are checked, loop 1 is terminated and the process is terminated. Thus, the process ends.

(7) Connection Information Deletion Process Flow Next, a process flow for deleting connection information will be described with reference to FIG. First, it is determined whether or not the connection period of the IP address being connected has exceeded a predetermined period (whether or not a timeout has been reached) (step S51). When the connection period of the connected IP dress exceeds the predetermined period (Y in step S51), a process for disconnecting the connection is performed (step S52). And the process which deletes the connection information of the IP address which disconnected is performed (step S53). That is, a process of deleting the IP address from which the connection has been disconnected and the domain and host corresponding to the IP address from the storage unit is performed. The process ends here.

4). Parallel Processing In this embodiment, when a plurality of e-mails addressed to the same domain are received, connections of a plurality of IP addresses may be established under predetermined conditions, and e-mails may be delivered in parallel.

  For example, in the case where tens of thousands of e-mails addressed to “xxx.co.jp” are accepted, if a single connection is delivered, the processing time becomes long and the processing load becomes high.

  Therefore, the mail server of this embodiment establishes connection of a plurality of IP addresses to one domain under a predetermined condition. For example, if delivery of the previous e-mail is not completed at the timing of delivery processing, it will be in a waiting state, so a new connection will be established so that it will not be in a waiting state. Control to use to deliver e-mail.

  In the present embodiment, when a new e-mail is received and a plurality of connections corresponding to the destination domain of the e-mail are held, any one that is not being delivered (free) Process to deliver e-mail using connection.

5. Example of using a connection pool for a specific domain In the present embodiment, in the case of e-mail addressed to a different domain, a connection corresponding to each domain is established, and the established connection is maintained. When an e-mail addressed to the same domain is received again, the processing load can be reduced and the e-mail can be efficiently delivered. However, if an e-mail addressed to the same domain is not accepted again within a predetermined period, the held connection is not used and only system resources are consumed.

  Therefore, in this embodiment, when it is expected that the number of e-mails delivered in a short time for a specific domain is expected, the connection pool may be controlled to be used only for the specific domain. Note that the number of specific domains may be one or more.

  For example, when it is expected that the number of electronic mails destined for a specific domain “xxx.co.jp” is large, a connection pool is set for an electronic mail addressed to a specific domain “xxx.co.jp”. For delivery to other domains, send e-mails to other domains by inquiring the DNS record host and IP address of the A record to the DNS server for each delivery without using the connection pool. You may control to deliver.

  In this embodiment, a specific domain may be explicitly specified in advance, or a domain in which a connection pool usage frequency can be expected to be higher than a predetermined value is dynamically acquired by a computer based on the connection status. You may control to.

In the present embodiment, the following method may be used in order to dynamically acquire a domain in which a connection pool usage frequency can be expected to be greater than or equal to a predetermined value based on the connection status.

  (1) From the past or current connection status (logs processed by the mail server, etc.), a domain that can be expected to have a usage frequency of a predetermined value or higher when it is targeted for a connection pool is acquired. For example, referring to the past or current connection status, a destination domain having a predetermined number or more (for example, 100 or more) of connections is acquired as a specific domain.

  (2) Buffering (storing) a delivery record in which a domain of an e-mail destination for a predetermined period (for example, 5 minutes) is recorded in the storage unit, and a plurality of identical domains exist from the buffered delivery record Get a domain. For example, referring to a delivery record in which the e-mail destination domains for the last five minutes from the current time are recorded, a destination domain having a predetermined number or more (for example, 10 or more) is acquired as a specific domain.

6). Example of further reducing MX record inquiries to the DNS server In this embodiment, the domain, host, and IP address of the connection information may not be deleted from the storage unit when the connection is disconnected. That is, connection information may be stored for use of a connection regardless of whether or not the connection is maintained. In this case, a connection status (connection flag) is added to the connection information, and it is determined whether or not the connection is maintained by referring to the connection status. For example, if the connection is maintained, the connection status (connection flag) is set to 1. If the connection is not held (when disconnected), the connection status (connection flag) is set to 0.

  When the newly received email destination domain is stored as a connection information domain or host in the storage unit, the connection status corresponding to the email destination domain (connection information domain or host) When the connection status is 1 (when the connection is held), the electronic mail is connected using the connection of the IP address corresponding to the destination domain (connection information domain or host) of the electronic mail. Process to deliver mail. The connection status is maintained at 1 while the connection is maintained, and the connection status is updated to 0 when the connection is disconnected.

  On the other hand, if the connection status corresponding to the domain of the email destination (connection information domain or host) is 0 (when the connection is disconnected), the email destination domain (domain of the connection information) Alternatively, the connection of the IP address corresponding to the host) is established, and after the connection is established, the electronic mail is delivered using the connection. Then, after the connection is established, the connection status is updated to 1. The connection status is maintained at 1 while the connection is held, and the connection status is updated to 0 when the connection is disconnected. In this way, even if the connection is disconnected, the MX record host acquisition process and the A record IP address acquisition process to the DNS server can be omitted, and the processing load can be reduced. it can.

10 mail server, 100 processing unit, 111 receiving unit, 112 connection pool unit, 114 connection information management unit, 115 delivery unit, 170 storage unit, 171 connection information, 180 information storage medium

Claims (8)

A program for a mail server that delivers electronic mail,
An accepting unit for processing to accept an e-mail;
A delivery unit that obtains a connection destination address from a DNS server based on the domain of the destination of the email, connects to the obtained connection destination address, and delivers the email;
A connection pool section that holds a connection to the connection destination address;
When the connection to the connection destination address is held, the computer is caused to function as a connection information management unit that performs processing for associating and storing the domain of the destination of the e-mail and the connection destination address in the storage unit. ,
The delivery unit is
When the newly accepted domain of the email destination is stored in the storage unit, a process of delivering the email using the connection of the connection destination address corresponding to the domain of the email destination A program characterized by that. In claim 1,
The connection information management unit
Processing for storing the domain of the e-mail destination, the host, and the connection destination address as a set in the storage unit when the host of the MX record can be obtained from the DNS server based on the domain of the e-mail destination And
When the MX record host cannot be obtained from the DNS server based on the domain of the email destination, the domain of the email destination is the host, the host and the connection destination address are associated with each other in the storage unit. Process to remember,
The delivery unit is
Deliver the e-mail using the connection of the connection destination address corresponding to the destination domain of the e-mail when the newly accepted e-mail destination domain is stored as a domain or host in the storage unit A program characterized by performing processing. In claim 1 or 2,
The connection information management unit
Processing for storing the domain of the e-mail destination, the host, and the connection destination address as a set in the storage unit when the host of the MX record can be obtained from the DNS server based on the domain of the e-mail destination And
When the MX record host cannot be obtained from the DNS server based on the domain of the email destination, the domain of the email destination is the host, the host and the connection destination address are associated with each other in the storage unit. Process to remember,
The delivery unit is
If the newly accepted email destination domain is not stored as a domain or host in the storage unit, the MX record host is acquired by the DNS server based on the newly accepted email destination domain. When the request is made and the host is acquired, the electronic mail is delivered using the connection of the connection destination address corresponding to the host when the host is stored as the host in the storage unit. A program characterized by performing processing. In any one of Claims 1-3,
The delivery unit is
When multiple emails addressed to the same domain are accepted, multiple connections are established for the domain under the specified conditions, and multiple emails are delivered in parallel.
The connection pool section
Keep multiple connections,
The connection information management unit
For each connection, perform a process of associating the destination domain of the e-mail with a connection destination address and storing it in the storage unit,
The delivery unit is
When a plurality of connection destination addresses for the destination domain of the newly received e-mail are stored in the storage unit, the process of delivering the e-mail using the connection of any connection destination address that is not being delivered The program characterized by performing. In any one of Claims 1-4,
The connection pool section
If the domain of the e-mail destination is a specific domain, hold the connection to the connection destination address based on the domain,
When the domain of the destination of the said e-mail is not a specific domain, the program cuts the connection to the said connection destination address based on the said domain after delivering the said e-mail. In any one of Claims 1-5,
The connection information management unit
A process of storing the domain of the destination of the email, the connection destination address, and a connection status indicating whether or not the connection is held in the storage unit as a set;
The delivery unit is
When the newly accepted domain of the destination of the email is stored in the storage unit, and the connection status corresponding to the domain of the destination of the email is information indicating that the connection is held Performs the process of delivering the email using the connection of the connection destination address corresponding to the domain of the destination of the email,
When the newly accepted domain of the destination of the email is stored in the storage unit, and the connection status corresponding to the domain of the destination of the email is information indicating that the connection is not held Performs a process of connecting to the connection destination address corresponding to the domain of the destination of the email and delivering the email,
The connection information management unit
When the connection to the connection destination address is held, the connection status corresponding to the domain of the e-mail destination is set to information indicating that the connection is held,
A program characterized in that, when the connection to the connection destination address is not held, the connection status corresponding to the domain of the destination of the e-mail is set to information indicating that the connection is not held. In any one of Claims 1-6,
The delivery unit is
Processing of delivering the e-mail using the connection of the connection destination address when the connection destination address acquired from the DNS server based on the newly received domain of the e-mail is stored in the storage unit The program characterized by performing. A mail server that delivers email,
An accepting unit for processing to accept an e-mail;
A delivery unit that obtains a connection destination address from a DNS server based on the domain of the destination of the email, connects to the obtained connection destination address, and delivers the email;
A connection pool section that holds a connection to the connection destination address;
A connection information management unit that performs processing for storing the destination domain of the e-mail and the connection destination address in association with each other when the connection to the connection destination address is held;
The delivery unit is
When the newly accepted domain of the email destination is stored in the storage unit, a process of delivering the email using the connection of the connection destination address corresponding to the domain of the email destination A mail server characterized by that.

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