JP2012039579A - Network communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily shorten time required for emails transmission/reception processing at a mail client.SOLUTION: A network communication device comprises: a communication interface for communication between a mail client and a mail server; a transmission mail proxy processing unit for receiving and storing transmission mails from the mail client as a proxy of the mail server, and also transferring the stored transmission mails to the mail server by accessing the mail server as a proxy of the mail client; and a reception mail proxy processing unit for receiving and storing reception mails from the mail server to a user of the mail client by accessing the mail server as a proxy of the mail client, and also transferring the stored reception mails to the mail client as a proxy of the mail server.

Description

  The present invention relates to a network communication device.

  Generally, e-mail transmission / reception processing by a mail client is realized by performing data communication between a mail client and a mail server on a network according to a protocol such as POP3 or SMTP. If a computer running a mail client is connected to a mail server on the network via a “slow line” such as an ISDN line or a mobile phone line, the time required for e-mail transmission / reception processing increases. There was room for improvement in terms of user convenience.

  Conventionally, in order to send and receive e-mail without registering e-mail users to a mail server published on the Internet, a first mail server published on the Internet receives the e-mail as a proxy, and a delivery destination database There is known an e-mail delivery system that determines a second mail server as a delivery destination with reference to, and delivers e-mail to the determined second mail server (see, for example, Patent Document 1).

JP 2002-223254 A

  In the above conventional system, the mail client receives the electronic mail delivered to the second mail server, and there is a possibility that the time required for the electronic mail receiving process may be shortened. However, in this system, it is necessary to prepare a delivery destination database and store it in the first mail server, or to incorporate a specially designed routine for each device, which complicates the configuration and processing. I was invited.

  SUMMARY An advantage of some aspects of the invention is that it provides a network communication device that can more easily shorten the time required for e-mail transmission / reception processing in a mail client.

  In order to solve at least a part of the above problems, the present invention can be realized as the following forms or application examples.

Application Example 1 A network communication device,
A communication interface for communication with a mail client on a network and a mail server for the mail client;
Sending mail proxy processing for receiving and storing outgoing mail from the mail client as a proxy for the mail server, accessing the mail server as a proxy for the mail client, and transferring the stored outgoing mail to the mail server And
Accessing the mail server as a proxy for the mail client, receiving and storing received mail addressed to the user of the mail client from the mail server, and storing the received mail as a proxy for the mail server A network communication apparatus comprising: a received mail proxy processing unit that transfers the message to a client.

  In this network communication device, the outgoing mail proxy processing unit receives and stores outgoing mail from the mail client as a proxy of the mail server, and accesses the stored mail to the mail server by accessing the mail server as the proxy of the mail client. The received mail proxy processing unit accesses the mail server on behalf of the mail client, receives and stores the received mail addressed to the user of the mail client from the mail server, and stores the stored received mail in the mail server. For transfer to the mail client as a proxy, for example, even if at least part of the line on the network path from the network communication device to the mail server is a slow line, the line with a slow processing time for mail transmission / reception in the mail client Existence of It does not increase by. Further, this network communication device functions as a proxy for the mail client and mail server without preparing and storing a delivery destination database or incorporating a specially designed dedicated routine. Therefore, in this network communication apparatus, the time required for the transmission / reception processing of the electronic mail in the mail client can be shortened more easily.

[Application Example 2] The network communication device according to Application Example 1,
The received mail proxy processing unit obtains a received mail list addressed to the user of the mail client when accessing the mail server, stores it as a received mail list for proxy processing, and receives a mail reception request from the mail client. In response, the proxy processing incoming mail list is sent to the mail client,
When the received mail proxy processing unit receives a specific mail deletion request from the mail client, the received mail proxy processing unit deletes the specific mail from the stored proxy processing received mail list and accesses the mail server. Then, the network communication device issues a request to delete the specific mail from the received mail list held by the mail server.

  In this network communication device, it is possible to prevent inconsistency between the proxy processing received mail list held by the network communication device and the received mail list held by the mail server, and the received mail is received again by the mail client. Therefore, user convenience can be further improved.

[Application Example 3] The network communication device according to Application Example 1,
The received mail proxy processing unit obtains a received mail list addressed to the user of the mail client when accessing the mail server, stores it as a received mail list for proxy processing, and receives a mail reception request from the mail client. In response, the proxy processing incoming mail list is sent to the mail client,
When the received mail proxy processing unit receives the mail reception request from the mail client, the received mail proxy processing unit accesses the mail server and receives the stored proxy processing received mail list in the mail server. A network communication device that sends the proxy processing received mail list to the mail client after matching with a mail list.

  In this network communication device, when receiving a mail reception request from a mail client, after matching the received mail list for proxy processing stored by accessing the mail server with the received mail list held by the mail server, Since the incoming mail list for proxy processing is sent to the mail client, even if a mail reception request by the mail client is issued during the inconsistency period between the incoming mail list for proxy processing and the received mail list, the mail client has already received it. It is avoided that the mail is received again, and the user convenience can be further improved.

Application Example 4 The network communication device according to any one of Application Examples 1 to 3, further comprising:
A DNS processing unit for accessing a DNS server on the network via the communication interface and converting a host name and an IP address;
The DNS processing unit, when receiving a DNS inquiry for inquiring an IP address of the mail server from the mail client, returns the IP address of the network communication apparatus itself.

  According to this network communication device, there is no need to change the settings of the mail sending server and the mail receiving server in the mail client depending on whether the mail client accesses the mail server via the network communication device. Can be further improved.

[Application Example 5] The network communication apparatus according to any one of Application Examples 1 to 4, further comprising:
It has an external device interface for connecting to an external storage device,
The outgoing mail proxy processing unit stores the received outgoing mail in the external storage device connected via the external device interface,
The received mail proxy processing unit stores the received mail received in the external storage device connected via the external device interface.

  In this network communication device, the capacity of the storage area of the network communication device can be saved, and the mail data is not lost even if the power of the network communication device is turned off, so that the mail can be reliably transmitted / received. Can do.

  The present invention can be realized in various modes. For example, a network communication device, a network communication system including the network communication device, a control method of these devices or systems, and a method of these methods, devices or systems. The present invention can be realized in the form of a computer program for realizing the function, a recording medium on which the computer program is recorded, and the like.

It is explanatory drawing which shows roughly the structure of the router 10 as a network communication apparatus in 1st Example of this invention. It is a flowchart which shows the flow of the mail transmission process in 1st Example. It is a flowchart which shows the flow of the mail reception process in 1st Example. It is a flowchart which shows the flow of the mail reception process in 1st Example. It is a flowchart which shows the flow of the mail reception process in 2nd Example. It is a flowchart which shows the flow of the mail reception process in 2nd Example.

Next, embodiments of the present invention will be described in the following order based on examples.
A. First embodiment:
A-1. Network communication device configuration:
A-2. Email sending process:
A-3. Email reception processing:
B. Second embodiment:
C. Variations:

A. First embodiment:
A-1. Network communication device configuration:
FIG. 1 is an explanatory diagram schematically showing the configuration of a router 10 as a network communication apparatus in the first embodiment of the present invention. The router 10 includes a control unit 100, a WAN interface 182, a LAN interface 184, and a USB interface 186.

  The LAN interface 184 is a communication interface that performs data communication with a node on the LAN side. The LAN interface 184 is connected to a personal computer PC and other network communication devices (for example, a hub). In the personal computer PC, an application program for sending and receiving e-mails operates on a predetermined operation system. Thereby, the personal computer PC functions as a mail client MC. Hereinafter, the personal computer PC functioning as the mail client MC is also simply referred to as a mail client MC.

  The WAN interface 182 is a communication interface that performs data communication with a WAN-side node. The WAN interface 182 is connected to another network communication device (for example, a modem) on the Internet INET side where the ISP server IS and the DNS server exist. In the ISP server IS, an application program for electronic mail delivery operates on a predetermined operation system. Thereby, the ISP server IS functions as a mail server MS. Hereinafter, the ISP server IS that functions as the mail server MS is also simply referred to as a mail server MS.

  The USB interface 186 is an interface for connecting a USB device. In this embodiment, a hard disk drive (external storage device) HDD as a USB device is connected to the USB interface 186.

  The control unit 100 is configured by a CPU and memory (ROM, RAM) (not shown) and controls the entire router 10. For example, the control unit 100 controls the LAN interface 184 and the WAN interface 182 to relay communication between the personal computer PC and the ISP server IS on the Internet INET. Further, the control unit 100 includes a DNS processing unit 110, an outgoing mail proxy processing unit 120, and a received mail proxy processing unit 130 as modules. Each element of the control unit 100 is realized by the CPU reading and executing a program corresponding to each element from the memory. The DNS processing unit 110 accesses a DNS server on the Internet INET and converts a host name and an IP address. The functions of the outgoing mail proxy processing unit 120 and the incoming mail proxy processing unit 130 will be described in detail in the description of the mail transmission process and the mail reception process described later.

A-2. Email sending process:
FIG. 2 is a flowchart showing the flow of mail transmission processing in the first embodiment. The mail transmission process of this embodiment is a process executed in the mail client MC, the router 10, and the mail server MS when the mail client MC transmits an electronic mail.

  In the mail transmission process of this embodiment, the outgoing mail proxy processing unit 120 of the router 10 receives and temporarily stores outgoing mail from the mail client MC on behalf of the mail server MS, and acts on behalf of the mail client MC. The transmitted mail is transmitted to the mail server MS at a predetermined timing. In the mail client MC, a router 10 is set as a mail transmission server.

  When the mail client MC receives a mail transmission instruction from the user, the mail client MC establishes a TCP connection with the router 10 registered as a mail transmission server (step S1). When a TCP connection is established between the mail client MC and the router 10, transmission mail data is transmitted from the mail client MC to the router 10 acting as a proxy for the mail server MS in accordance with a predetermined protocol for mail transmission such as SMTP. . That is, the mail client MC transmits a call message (step S2), the outgoing mail proxy processing unit 120 of the router 10 responds to reception (step S3), and the mail client MC transmits mail sender information (step S4). The outgoing mail proxy processing unit 120 responds to reception (step S5), the mail client MC transmits mail recipient information (step S6), the outgoing mail proxy processing unit 120 responds to reception (step S7), and the mail client MC The transmission mail body is transmitted (step S8), the transmission mail proxy processing unit 120 makes a reception response (step S9), the mail client MC transmits a communication end request (step S10), and the transmission mail proxy processing unit 120 receives the response. (Step S11), and the TCP session is disconnected (step S11). Flop S12). In each of the above processes, the router 10 stores transmission mail data (mail sender information, mail receiver information, transmission mail text, etc.) received from the mail client MC in a predetermined storage in the hard disk drive HDD via the USB interface 186. Store in the area. Note that the processing from step S4 to S8 is repeatedly executed by the number of outgoing mails.

  The router 10 accesses the mail server MS at a predetermined timing and establishes a TCP connection with the mail server MS (step S21). The predetermined timing may be a timing after a predetermined time has elapsed since the TCP session between the router 10 and the mail client MC is disconnected, or a timing when a predetermined time has been reached. Alternatively, it may be a timing every elapse of a predetermined interval time.

  When a TCP connection is established between the router 10 and the mail server MS, the hard disk drive HDD of the router 10 is transferred from the router 10 acting as a mail client MC to the mail server MS according to a predetermined protocol for mail transmission such as SMTP. The outgoing mail data stored in is sent. That is, the outgoing mail proxy processing unit 120 of the router 10 transmits a call message (step S22), the mail server MS receives a response (step S23), and the outgoing mail proxy processing unit 120 transmits mail sender information (step S22). S24), the mail server MS receives and responds (step S25), the outgoing mail proxy processing unit 120 transmits the mail recipient information (step S26), the mail server MS receives and responds (step S27), and the outgoing mail proxy process The unit 120 transmits the transmission mail text (step S28), the mail server MS receives a response (step S29), the transmission mail proxy processing unit 120 transmits a communication end request (step S30), and the mail server MS receives the reception response. Then, the TCP session is disconnected (step S32). Note that the processing from step S4 to S8 is repeatedly executed by the number of outgoing mails. Through the above processing, the outgoing mail from the mail client MC is finally received by the mail server MS.

  As described above, in the mail transmission process of the first embodiment, a transmission mail from the mail client MC is received by the router 10 acting as a proxy for the mail server MS, temporarily stored in the hard disk drive HDD, and at a predetermined timing. The data is transmitted from the router 10 acting as a proxy for the mail client MC to the mail server MS. The process that the mail client MC is involved in when sending mail is only the process between the mail client MC and the router 10 (steps S1 to S12 in FIG. 2), and between the router 10 and the mail server MS. The mail client MC is not involved in the process (steps S21 to S32 in FIG. 2). Therefore, for example, even when at least part of a line on the network path from the router 10 to the mail server MS (ISP server IS) is a “slow line” such as an ISDN line or a mobile phone line, the mail client The processing time for mail transmission in the MC is not increased by the existence of the “slow line”. Therefore, in the mail transmission process of the first embodiment, it is possible to suppress an increase in the time required for the e-mail transmission process in the mail client MC, and to improve user convenience.

  In the mail transmission process according to the first embodiment, the transmission mail data received by the router 10 is stored in the hard disk drive HDD connected via the USB interface 186, so that the capacity of the storage area of the router 10 is increased. Can be saved. Further, since the transmitted mail data is not lost even when the router 10 is turned off, the mail can be transmitted reliably.

A-3. Email reception processing:
3 and 4 are flowcharts showing the flow of mail reception processing in the first embodiment. The mail reception process of this embodiment is a process executed in the mail client MC, the router 10 and the mail server MS when the mail client MC receives an electronic mail addressed to the user of the mail client MC.

  In the mail receiving process of this embodiment, the router 10 receives and temporarily stores the received mail addressed to the user of the mail client MC from the mail server MS on behalf of the mail client MC, and responds to the request from the mail client MC. In response, the received mail is transmitted to the mail client MC on behalf of the mail server MS. In the router 10, information necessary for proxy reception of received mail addressed to the user of the mail client MC (for example, user name, password, port number, deletion flag, reception interval) and the like are registered in advance. The mail client MC is set with a router 10 as a mail receiving server.

  The router 10 accesses the mail server MS at a predetermined timing, and establishes a TCP connection with the mail server MS (step S41). Note that the predetermined timing may be a timing when a preset time is reached, or may be a timing at every elapse of a predetermined interval time.

  When a TCP connection is established between the router 10 and the mail server MS, the received mail data addressed to the user of the mail client MC is sent from the mail server MS to the mail client MC according to a predetermined protocol for receiving mail such as POP3 and IMAP. Is transmitted to the router 10 acting as a proxy. That is, the received mail proxy processing unit 130 of the router 10 transmits mail recipient information (step S42), the mail server MS requests a password (step S43), and the received mail proxy processing unit 130 transmits a password (step S42). S44), the received mail proxy processing unit 130 acquires information about the received mail (number and size of received mail, received mail list) from the mail server MS (step S45), and the received mail proxy processing unit 130 receives the received mail from the mail server MS. The main body is downloaded (step S46), the mail server MS sends a completion response (step S47), the received mail proxy processing unit 130 transmits a communication end request (step S48), and the TCP session is disconnected (step S49). In each of the above processes, the router 10 stores the received mail data (received mail list, received mail text, etc.) received by proxy from the mail client MC in a predetermined storage area in the hard disk drive HDD via the USB interface 186. In the present specification, the mail list acquired and stored in the router 10 is referred to as a “proxy processing received mail list”.

  When the mail client MC receives a mail reception instruction from the user, the mail client MC establishes a TCP connection with the router 10 registered as a mail reception server (step S61). When a TCP connection is established between the mail client MC and the router 10, the received mail data addressed to the user of the mail client MC acts as a proxy for the mail server MS in accordance with a predetermined protocol for receiving mail such as POP3 and IMAP. 10 to the mail client MC. That is, the mail client MC transmits mail recipient information (step S62), the received mail proxy processing unit 130 of the router 10 requests a password (step S63), and the mail client MC transmits a password (step S64). The mail client MC acquires information about the received mail (number and size of received mail, received mail list for proxy processing) from the router 10 (step S65), and the mail client MC downloads the received mail text from the router 10 (step S66). . Here, when the mail client MC issues a deletion request for the specific mail (mail 1) according to the user's instruction (step S67), the received mail proxy processing unit 130 deletes the specific mail from the proxy processing received mail list. A completion response is sent (step S68), the mail client MC transmits a communication end request (step S69), and the TCP session is disconnected (step S70).

  When a specific mail is deleted in the TCP connection between the mail client MC and the router 10, the router 10 sends a mail for deleting the specific mail in the received mail list held by the mail server MS. The server MS is accessed and a TCP connection is established with the mail server MS (step S91). When a TCP connection is established between the router 10 and the mail server MS, a specific mail in the received mail list held by the mail server MS is deleted according to a predetermined protocol for receiving mail such as POP3 and IMAP. Is called. That is, the received mail proxy processing unit 130 of the router 10 transmits mail recipient information (step S92), the mail server MS requests a password (step S93), and the received mail proxy processing unit 130 transmits the password (step S92). S94), the received mail proxy processing unit 130 obtains information about the received mail (number and size of received mails, received mail list for proxy processing) from the mail server MS (step S95), and the received mail proxy processing unit 130 receives the specific mail. (Step S96), the mail server MS deletes the specific mail from the received mail list and responds with completion (step S97), and the received mail proxy processing unit 130 transmits a communication end request (step S98). ), The TCP session is disconnected (step S99). Note that, when a specific mail is not deleted in the TCP connection between the mail client MC and the router 10, it is necessary to delete a specific mail in the received mail list held by such a mail server MS. No processing is performed.

  As described above, in the mail reception process of the first embodiment, the received mail addressed to the user of the mail client MC is received from the mail server MS by the router 10 acting as a proxy for the mail client MC and temporarily stored in the hard disk drive HDD. In response to a mail reception request from the mail client MC, the mail is sent from the router 10 acting as a proxy for the mail server MS to the mail client MC. The process that the mail client MC is involved in receiving the mail is only the process between the mail client MC and the router 10 (steps S61 to S70 in FIG. 3), and between the router 10 and the mail server MS. The mail client MC is not involved in the process (steps S41 to S49 in FIG. 3). Therefore, for example, even when at least part of a line on the network path from the router 10 to the mail server MS (ISP server IS) is a “slow line” such as an ISDN line or a mobile phone line, the mail client The processing time for mail reception in the MC is not increased by the existence of the “slow line”. Therefore, in the mail receiving process of the first embodiment, it is possible to suppress an increase in the time required for the e-mail receiving process in the mail client MC, and to improve user convenience.

  In the mail receiving process of the first embodiment, when a mail deletion request is issued from the mail client MC to the router 10, the received mail proxy processing unit 130 receives the proxy processing received mail list held by the router 10. The specific mail is deleted from the mail server MS, and a request for deleting the specific mail from the received mail list held by the mail server MS is issued to the mail server MS. For this reason, in the mail receiving process of the first embodiment, it is possible to prevent inconsistency between the proxy processing received mail list held by the router 10 and the received mail list held by the mail server MS. It is avoided that the received mail is received again, and the user convenience can be further improved.

  In the mail receiving process of the first embodiment, since the received mail data received by the router 10 is stored in the hard disk drive HDD connected via the USB interface 186, the capacity of the storage area of the router 10 is increased. Can be saved. In addition, since the received mail data is not lost even when the power of the router 10 is turned off, the mail can be reliably received.

B. Second embodiment:
5 and 6 are flowcharts showing the flow of mail reception processing in the second embodiment. In the mail reception process of the second embodiment, when the router 10 receives a mail reception request from the mail client MC, the proxy processing reception mail list held by the router 10 is matched with the reception mail list held by the mail server MS. The point that the proxy processing received mail list is transmitted from the router 10 to the mail client MC after the processing (steps S141 to S146 in FIG. 5) is performed is different from the first embodiment. Other points are the same as in the first embodiment.

  That is, when the mail client MC issues an acquisition request for information related to received mail (the number and size of received mail, the received mail list for proxy processing) to the router 10 as a mail reception request (step S65 in FIG. 5). The router 10 accesses the mail server MS and establishes a TCP connection with the mail server MS (step S141). When a TCP connection is established between the router 10 and the mail server MS, the mail server MS holds a proxy processing received mail list held by the router 10 according to a predetermined protocol for receiving mail such as POP3 and IMAP. Processing to match the received mail list is performed. That is, the received mail proxy processing unit 130 of the router 10 transmits mail recipient information (step S142), the mail server MS requests a password (step S143), and the received mail proxy processing unit 130 transmits a password (step S142). In step S144, the received mail proxy processing unit 130 acquires information related to the received mail (the number and size of received mails and the received mail list) from the mail server MS (step S145). The received mail proxy processing unit 130 transmits the acquired received mail list to the mail client MC as the latest proxy processing received mail list (step S146). The subsequent processing (the processing after step S66 in FIG. 6) is the same as that of the first embodiment.

  For example, when the user of the mail client MC accesses the mail server MS without going through the router 10 to receive a specific received mail and deletes the received mail, such as when the mail is received on the go, There is a period in which the proxy processing received mail list held by the router 10 is not consistent with the received mail list held by the mail server MS. In the mail receiving process of the second embodiment, when the router 10 receives a mail reception request from the mail client MC, the proxy processing received mail list held by the router 10 is matched with the received mail list held by the mail server MS. After the processing is performed, since the proxy processing received mail list is transmitted from the router 10 to the mail client MC, the mail reception request by the mail client MC is in a mismatch period between the proxy processing received mail list and the received mail list. Even when issued, it is avoided that the received mail is received again by the mail client MC, and user convenience can be further improved.

C. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

C-1. Modification 1:
The configuration of the router 10 in each of the above embodiments is merely an example, and various modifications can be made. In each of the above embodiments, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. Also good. In addition, when part or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, a hard disk It also includes an external storage device fixed to the computer.

C-2. Modification 2:
In each of the above embodiments, the transmission mail data and the reception mail data are stored in the storage area in the hard disk drive HDD via the USB interface 186, but the transmission mail data and the reception mail data are other than the hard disk drive HDD. It may be stored in a predetermined storage area (for example, a memory included in the router 10).

C-3. Modification 3:
In each of the above embodiments, the router 10 is set as the mail transmission server and the mail reception server in the mail client MC, but the mail server MS is set as the mail transmission server and the mail reception server in the mail client MC. Also good. Even in such a case, when the DNS processing unit 110 of the router 10 receives a DNS inquiry for inquiring about the IP address of the mail server MS from the mail client MC, by returning the IP address of the router 10 itself, The outgoing mail proxy processing unit 120 and the received mail proxy processing unit 130 of the router 10 can function as a proxy for the mail server MS. In this way, it is not necessary to change the settings of the mail transmission server and the mail reception server in the mail client MC depending on whether the access from the mail client MC to the mail server MS is through the router 10 or not. Can be further improved.

C-4. Modification 4:
In each of the embodiments described above, the router 10 records and stores a history of received mail and / or transmitted mail in, for example, the hard disk drive HDD, and displays the statistical processing result of the mail history on the display device of the personal computer PC or the router 10. It is good. Examples of the mail history statistical processing result include the number of mails for each destination, the number of mails for each sender, and the number of mails for each time zone. In this way, it is possible to easily grasp the tendency related to received mail and / or sent mail (for example, who is the sender of the received mail and who is the destination of the sent mail). Can do. The router 10 may receive a restriction instruction from the user, and may reject reception of received mail or prohibit transmission of outgoing mail according to the restriction instruction. In this case, a restriction instruction tool such as a check box may be displayed on the mail history statistical processing result display screen so that the user can issue a restriction instruction using the tool.

C-5. Modification 5:
The present invention is applicable not only to the router 10 but also to other types of devices (for example, a switch, a wireless LAN access point, etc.) as long as it functions as a network communication device that performs communication in a predetermined network.

DESCRIPTION OF SYMBOLS 10 ... Router 100 ... Control part 110 ... DNS processing part 120 ... Outgoing mail proxy processing part 130 ... Incoming mail proxy processing part 182 ... WAN interface 184 ... LAN interface 186 ... USB interface

Claims (5)

A network communication device,
A communication interface for communication with a mail client on a network and a mail server for the mail client;
Sending mail proxy processing for receiving and storing outgoing mail from the mail client as a proxy for the mail server, accessing the mail server as a proxy for the mail client, and transferring the stored outgoing mail to the mail server And
Accessing the mail server as a proxy for the mail client, receiving and storing received mail addressed to the user of the mail client from the mail server, and storing the received mail as a proxy for the mail server A network communication apparatus comprising: a received mail proxy processing unit that transfers the message to a client. The network communication device according to claim 1,
The received mail proxy processing unit obtains a received mail list addressed to the user of the mail client when accessing the mail server, stores it as a received mail list for proxy processing, and receives a mail reception request from the mail client. In response, the proxy processing incoming mail list is sent to the mail client,
When the received mail proxy processing unit receives a specific mail deletion request from the mail client, the received mail proxy processing unit deletes the specific mail from the stored proxy processing received mail list and accesses the mail server. Then, the network communication device issues a request to delete the specific mail from the received mail list held by the mail server. The network communication device according to claim 1,
The received mail proxy processing unit obtains a received mail list addressed to the user of the mail client when accessing the mail server, stores it as a received mail list for proxy processing, and receives a mail reception request from the mail client. In response, the proxy processing incoming mail list is sent to the mail client,
When the received mail proxy processing unit receives the mail reception request from the mail client, the received mail proxy processing unit accesses the mail server and receives the stored proxy processing received mail list in the mail server. A network communication device that sends the proxy processing received mail list to the mail client after matching with a mail list. The network communication device according to any one of claims 1 to 3, further comprising:
A DNS processing unit for accessing a DNS server on the network via the communication interface and converting a host name and an IP address;
The DNS processing unit, when receiving a DNS inquiry for inquiring an IP address of the mail server from the mail client, returns the IP address of the network communication apparatus itself. The network communication device according to any one of claims 1 to 4, further comprising:
It has an external device interface for connecting to an external storage device,
The outgoing mail proxy processing unit stores the received outgoing mail in the external storage device connected via the external device interface,
The received mail proxy processing unit stores the received mail received in the external storage device connected via the external device interface.

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