JPH0310539A - Electronic mail system - Google Patents

Abstract

PURPOSE:To improve the reliability of a mail system by depositing a mail to a terminal equipment to receive the mail and storing it as the mail when the terminal equipment to receive the mail cannot receive the mail and delivering the deposited mail when the restoration notice is received from the terminal equipment. CONSTITUTION:When an access comes from an outgoing terminal equipment, all data are fetched and a mail is delivered to a designated terminal equipment. When the delivery is not normally finished but subjected to center deposit, an unarrived notice CD is generated and sent to the outgoing terminal equipment. The center equipment recognizes that the outgoing terminal equipment sending the terminal restoration is restored normally at present and the transmission/reception are enabled, then the presence of the mail of center deposit is checked from the reception information of a center deposit mail management table and the mail is sent to the terminal equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic mail system comprising a plurality of mail communication terminals and a center device having a mail storage and exchange function.

[Prior Art] In recent years, systems for digitizing mail, which was traditionally delivered manually, have become popular for the purpose of reducing office expenses and improving timeliness.

In particular, systems in which each terminal transfers messages via a center device with a store-and-forward function provide a wide variety of mail services such as instant delivery, broadcast, time-specified delivery, confidential, mailbox, and bulletin board services.

Among these services, when using the instant delivery, timed delivery, and circular mail services, when you send a message, if the recipient's terminal is busy, it enters redial mode and cannot send the message until the recipient's terminal is free. condition was occurring. Furthermore, when sending a plurality of images, if the other party's terminal does not have a large-capacity buffer memory, there is the inconvenience of having to wait until all images are output.

However, mail services that have a store-and-forward function do not have the above-mentioned troubles (and have the advantage of being able to finish the sending operation and move on to the next operation without being restricted by the conditions of the recipient's terminal. If you put mail in the other party's mailbox, you can retrieve the mail from your own mailbox whenever necessary from any terminal connected to the system, regardless of location. .Especially in the case of confidential mail, it cannot be withdrawn without entering the PIN number, so the mail can only be delivered to a specific person and confidentiality can be maintained.

In addition, bulletin board services provide unique services for store-and-forward message communication, such as the ability to provide messages to an unspecified number of people. Furthermore, if the other party's terminal becomes unable to send mail, there is a function to send mail to a substitute terminal for that terminal, and if there is no substitute terminal or it is not possible to send mail to a substitute terminal, the center device will not be able to send mail until the terminal becomes ready to receive. It is also possible to have a function that allows mail to be temporarily stored (hereinafter referred to as center storage) and retrieved from another terminal.

[Problems to be Solved by the Invention] However, in the above conventional example, in the case of the center storage function, even if a terminal that cannot send is restored, the center device cannot recognize it, so even if the terminal is normal, the center storage function is not used. email could not be sent to that device. Currently, as a countermeasure, if there is any kind of access (related to mail service) from the terminal to the center device,
The center device determines that the terminal that was down has started up normally, and sends mail to that terminal. However, if a terminal that is down does not access the center device, the mail remains in the custody of the center, and the automatic distribution function cannot be fully utilized.

Furthermore, since the state of each terminal is expected to change during communication between the center device and the terminal, it is also necessary for the center device to manage and reflect this as a management table.

The present invention was made to solve the above problems, and
To provide an e-mail system that can directly deliver center-received mail addressed to a terminal that is unable to communicate to the restored terminal after the terminal is restored.

Another object is to provide an e-mail system that can update a management table based on information when delivery failure occurs during communication between a center device and a terminal.

[Means and operations for solving the problems] In order to achieve the above object, the e-mail system of the present invention has the following configuration. That is, in an e-mail system consisting of a plurality of e-mail communication terminals and a center device having an e-mail storage/exchange function, when a terminal that should receive e-mail cannot receive the e-mail, means for storing e-mail sent to the terminal as e-mail; When you receive a notification from your device that it has been restored,
It has means for searching for retained mail, and means for delivering the retained mail to the terminal when the retained mail is found as a result of the search.

Preferably, the center device also includes means for accumulating status information of mail communication terminals, and means for determining, when a message is received from a mail communication terminal whose delivery was not possible, that this is a recovery message.

More preferably, the distribution is performed in response to a request from a sending terminal.

Further, an e-mail device according to another invention has the following configuration. That is, in an e-mail system consisting of a plurality of mail communication terminals and a center device having a mail storage and forwarding function, the center device has a management table for managing the communication enabled/disabled states of the mail terminals, and a and means for updating the table based on the information.

Preferably, when a communication failure occurs between the center device and a mail communication terminal, the management table is updated by the mail communication terminal, and when the communication failure state is restored, the management table is updated by the recovered terminal. It is characterized by

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

<Description of Configuration (FIGS. 1 and 2)> FIG. 1 is a system configuration diagram of the e-mail system in this embodiment. In the figure, 1 to 4 are equipped with applications that can send and receive e-mail, text data,
This includes email communication terminals that can handle image data and other media data, such as telematic terminals. 5 is a center device which has various management functions such as storage and exchange of e-mail and terminal or personal ID, and provides various e-mail services to each e-mail communication terminal;
6 is a network that allows each of the mail communication terminals 1 to 4 and the center device 5 to communicate with each other. Network 6 includes PSTN (telephone network) and PSPDN if it is a wide area network.
(packet switched network).

There are PSCDN (circuit switched networks), leased lines, etc.

If it is a private network, it is a local area network or PBX.
, there is a private line within the premises. Reference numeral 7 designates a central processing unit that controls all the devices in the center device 5. Reference numeral 8 designates a main storage device that temporarily stores mail control information and mail body information, stores various management tables, or is used as a work area. Reference numeral 9 denotes a large-capacity storage device used as a backup for a large amount of mail, mailboxes, various information, or programs, and its storage media include optical disks, magnetic disks, magneto-optical disks, and magnetic tapes.

IO is a program storage device that stores control programs and application programs with email functions necessary to operate the system, and 11 is an input/output device such as a console and printer used for system management, power monitoring and backup. It is a peripheral device including a power supply device such as a power supply. 12 is a communication control device that controls communication with each mail communication terminal 1 to 4, and is connected to the network 6 described above.
It performs interface matching with the terminals, link control to establish connections with each terminal 1 to 4, network control to receive and receive data and secure communication channels, etc.

FIG. 12 is a diagram showing the internal configuration of the mail communication terminal in this embodiment.

In the figure, 13 is a central processing unit that controls the entire system of mail communication terminals, 14 is a main storage unit that stores control programs necessary for system operation and mail function processing programs, and is used as a work area. This is a large-capacity storage device that stores media data handled by this terminal, and also stores information about email bodies. 16 is an output unit that outputs media data handled by this terminal, and CR
Display on a screen such as T or LCD, output to paper or photosensitive paper, and in the case of audio data, output from a speaker. 17 is an input section for inputting media data handled by this terminal, and is a keyboard.

Touch sensor, digitizer, photoreceptor, image sensor (CO
D, image pickup tube, etc.), in the case of audio data,
There is input via microphone. Reference numeral 18 denotes a communication control device that controls communication with the center device 5 via the network 6, and performs interface matching with the network 6 described above, link control to establish a connection with the center device 5, data transmission/reception, and securing a communication path. Performs network control, etc.

Next, in the system configuration shown in FIG.
When the user 4 requests a mail service from the center device 5, it is necessary to exchange not only the main text of the mail but also control information for the mail instructing how to process the mail.

Explanation of control information (Figure 3)> Here, Figure 3 is a diagram showing an example of this, and for convenience of explanation, the explanation will be based on this, but the format and contents are limited to this. isn't it.

As illustrated, the mail service identifier 30 indicates the content of the service. For example, services such as instant delivery, inserting/withdrawing mailboxes, inserting/withdrawing mailboxes, bulletin boards, and various make-shift requests have information encoded so that they can be identified between terminals and center equipment. be. Similarly, the mail service additional information 31 includes, for example, even if the mail service identifier is immediate delivery, the priority of the mail, simultaneous delivery in the case of multiple recipients, time specification, presence or absence of delivery confirmation, proxy terminal information, etc. This is information for specifying the presence or absence, etc., as necessary. The mail sender information 32 includes information such as the sender's name, affiliation name, and sender terminal name, which is necessary for the recipient to identify the sender. The mail sending time 33 is for notifying the recipient of the time when the mail was sent. If the receiving terminal is unable to deliver from the center equipment due to a malfunction and the data is held at the center, or if the recipient needs to access and retrieve the information such as a mailbox or confidential box, this information can be used to determine when the transmission was sent. You can tell if it's an email.

Next, the mail recipient information 34 is necessary information when the center device specifies the delivery destination when delivering the mail, and is also important information to ensure that it is passed to the recipient even after the mail is delivered. . The mail delivery time 35 is used to inform the recipient of the time when the mail was received, but even if the center device delivers the mail to the designated receiving terminal, it is not actually delivered to the recipient. This information is necessary because there is a delay before the information is available. Also, as for the information in the email body, first of all,
The subject of the email 36, the amount of information in the email body (in the case of an email communication terminal, it may be expressed in pages), the type of media (broadly divided into image data, text data, audio data, etc.) Among them, G
3 facsimile, MH code such as G4 facsimile, M
There is also a classification based on encoding methods for data compression such as R code and MMR code. ) The email control information shown in FIG. 3 mentioned above is hereinafter referred to as a control document (CD).

The mail body for this CD is called a normal document (ND).

<Explanation of communication format (Figure 4)> Next, when performing email communication between the terminal and the center device, the format shown in Figure 4 (a)
It is formatted and sent out as shown in (C). This is a format used in HDLC communication procedures, and F2O is called a flag and is used to identify the beginning and end of this data. The data is "01111110", and "0" is inserted or deleted in order to prevent this pattern from occurring in other than flags, thereby maintaining data transparency. Next, A41 is
address, but not the sender's address, the network (
It is used to perform the following identification when transmitting and receiving data between a network) and a terminal device (or center device).

When A=“l 1000000”, DCE to DTE
As a command or response to A="10000
000'', it is used as a command or response from the DTE to the DCE.Next, C42 is a controller section, and ■(information) frame (DATA)
, S (monitoring) frame (RR, RNR, REJ),
IJ (off duty) frame (SABM, UA, DM,
DISC.

FRMR) is used to identify each frame. There is a P/F bit in this, and if the P bit (ball) is set to "1", it is necessary to set the F bit (final) to "1" and return it.

When transmitting and receiving data between the terminal and the center device, the communication control unit 43 negotiates data format specifications and media type during call setup/cancellation and data transfer between the terminal and the center device. In addition, an identifier is inserted to perform controls such as confirmation of reception for each data transfer unit such as page or block, and request for retransmission of data in the event of an error.

This control content and procedure is determined by CCITT and ISO.
Standardization is progressing e O3I (0pen S
3rd layer (network layer), 4th layer (transport layer), 5th layer (
This corresponds to what is specified in the session layer).

The network layer performs this setting/cancellation, the transport layer performs network quality checks and settings via other networks, and the session layer performs data transfer type negotiation and confirmation/retransmission of data transfer in units of pages and blocks. Related controls are specified. Next, FC345 is a frame check sequence and has a function of checking whether data is correct or incorrect. However, since there is no correction function, if there is an error, a retransmission request is made and the data is retransmitted.

Next, the user data section 44 is used when the terminal side (user side) rather than the network sends data to the other party's terminal (other user). Alternatively, it is also used by the network to provide optional additional services to users. The service may include, for example, an extended address,
There are extension addresses, etc. FIG. 4(b) shows a communication data format when transmitting a CD. Then, the CD which is the mail control information shown in FIG. 3 is inserted into the user data section 44. Moreover, FIG. 4(C) shows the communication data format when transmitting ND. Similarly, ND, which is the information of the mail body, is inserted into the user data section 44.

<Description of Communication Procedure (FIGS. 5 to 7)> Next, FIG. 5 is a diagram showing a data communication procedure related to network control between each of the terminals 1 to 4 and the center device 5. As shown in the figure, when a terminal accesses a center device to transfer data, the terminal first requests the network to make a call, and the network outputs an incoming call to the center device. The center device receives this incoming call and returns an incoming call acceptance message to the network, and the network receives this and returns a connection completion message to the terminal. Through this process, a call is established between the terminal and the center device, and data transfer becomes possible. Thereafter, when data transfer is finished, the terminal issues a recovery request to the network, and the network outputs a disconnection instruction to the center device. The center device receives this disconnection instruction and returns a disconnection confirmation to the network, and the network receives this and returns a restoration confirmation to the terminal.

Next, FIG. 6 is a diagram showing a data communication procedure during data transfer after a call is established. First, as shown in Figure 5, when a call is established and data communication becomes possible between the terminal and the center equipment, the type of the other party's terminal is confirmed as shown in Figure 6.
Establish a session connection to confirm the data exchange conditions.

When a session connection is sent from the terminal to the center device,
Upon receiving this, a confirmation is returned from the center device to the terminal. Then, by sending the CD (control document) and ND (normal document), a request for mail service is made from the terminal to the center device, and in response to the request, the center device returns acceptance of the service. Here, if there is no data to be continuously transferred from the terminal side or if there is no data to be transferred from the center device, a session disconnection message is sent to the center device to cancel the session connection. In response to this, the center device returns completion, and through this series of communication procedures, the request and reception of the mail service from the terminal to the center device and the transfer of the mail body are completed. When the data transfer shown in Fig. 5 is completed, the above-mentioned recovery request, disconnection instruction, disconnection confirmation, and recovery confirmation are respectively sent to cancel the call established between the terminal and the center device, and the call is disconnected. . On the other hand, the center device decodes the sent CD and executes the service in response to the service request. For example, in the case of instant distribution shown in FIG. 6, the center device directs the sending terminal to the destination terminal specified by the
The call setting shown in FIG. 5 is performed, and when the call is established, a session connection is executed.

Then, after transmitting the CD and the ND which is the body of the received mail, and receiving an acceptance for the CD and ND from the destination terminal, the session is disconnected and the call disconnection procedure is executed. In this way, the instant delivery mail service requested by the originating terminal is completed.

In the following, descriptions of call setup/disconnection, session connection/disconnection, CD/ND reception, etc. will be omitted since they are the same.

FIG. 7 shows a data communication procedure during data transfer in the mailbox service. When the originating terminal makes a mailbox request to the center device using a CD and sends an ND, the center device receives this and posts this ND to the designated mailbox. When the mailbox catalog inquiry CD is accessed from the destination terminal, the center device transmits the CD including the list in the supplementary information 39 of FIG. 3 to the destination terminal. Furthermore, if there is a request from the destination terminal to retrieve mail in the mailbox using a CD, the mail is sent to the destination terminal. and,
Mailbox service completes.

Description of Management Tables (FIG. 8)> Next, various management tables defined within the center device will be described.

FIGS. 8(a) to 8(e) show typical management tables in this embodiment. and Fig. 8(a) and (b)
) are attribute management tables, and FIGS. 8(C) to (e)
is the mail management table. This Figure 8(a) is
This is a terminal management table in which information about all terminals connected to the center device is managed. When running the mail service, this table is always referenced.
It is possible to confirm the sender and recipient, confirm device information, and send on behalf of the sender. FIG. 8(b) is a user management table in which the personal identification number used when making a withdrawal from a confidential mailbox, the terminal to which the person belongs, or the personal ID, etc. are managed. It also enables security and email communication between people, rather than machine-to-machine.

Further, FIG. 8(C) is a mailbox management table, in which control information of mails posted in each mailbox, memory space of storage location, etc. are managed. This table is then referenced when inquiring about the mailbox list or registering/withdrawing a mailbox. FIG. 8(d) is a management table for confidential boxes, in which the same contents as mailboxes are managed for each confidential box. Note that this confidential email can only be withdrawn by the person in question using his or her personal identification number.

For this purpose, the password is also managed in this table. Figure 8(e) shows a function that stores mail in the center device so that when mail cannot be sent to the destination terminal, it can be sent after waiting for the terminal to recover, or retrieved from another terminal. This table is required when the data center has a management table, and is called the center storage management table. in this case,
Unlike mailboxes and confidential boxes, the above-mentioned boxes are not prepared and are managed on a per-mail or per-terminal basis. Other than that, it is the same as that in FIG. 8(C), and is referred to when making an inquiry about the center custody list or withdrawing center custody mail.

Description of Processing Procedure (FIGS. 9 to 18) Next, the processing procedure of the center device in this embodiment will be explained below with reference to the flowcharts shown in FIGS. 9 to 18. Note that Figures 9 to 15 are the main routine, and the first
6 to 18 are subroutines called by the main routine.

First, in FIG. 9, when there is an access from the originating terminal, all data is captured and the above-mentioned CD is stored. After that, if there is an ND, the ND is also stored in the same way. In the case of a CD, the data is stored in the main storage device, and in the case of an ND, the data is stored in either the main storage device or the mass storage device. Once stored, the CD is decrypted and each mail service is executed according to the decrypted results. for example,
For immediate delivery, go to Figure 10, for confidential, go to Figure 11, for mailbox, go to Figure 12, for device recovery, go to Figure 13, for center storage, go to Figure 14, for inquiries. If so, the process proceeds to FIG. 15.

In the case of immediate delivery, as shown in Figure 10, it is first determined whether or not it is a broadcast based on whether or not multiple receiving terminals are specified, and if it is a broadcast, it is sent to all specified terminals. Mail is delivered either sequentially or simultaneously, and if it is not a broadcast, the mail is delivered to the specified terminal. If the distribution ends normally, the process proceeds to the next step, and if it does not end normally, retransmission processing is performed.

In this retransmission process, if the retransmission process ends normally, proceed to the next step, and if it does not end normally, the center storage process is performed and the next step proceeds.In the 0th order judgment process, the presence or absence of a delivery confirmation request is checked, and if there is no delivery confirmation request, End immediate distribution. However, in the case of a delivery request, if the above delivery results are normal, a delivery confirmation notice CD will be created, and if the delivery result is not completed normally and the CD is kept at the center, a non-delivery notice will be created. Create a CD and send it to the originating terminal. If this transmission process ends normally, the immediate delivery ends, but if it does not end normally, a retransmission process is performed, and if it still does not end normally, the center storage process is performed and the immediate delivery process is performed. end.

Note that the retransmission process and the center storage process are each subroutines, which will be explained later.

Next, if it is confidential, check whether it is inserted or withdrawn, as shown in Figure 11. First, to explain the input case, check the recipient and terminal from the information on the CD, and input the received mail (ND) into the confidential box registration number registered in the user management table shown in Figure 8(b). do. When the mail is input, additional registration is performed in the confidential box mail management table shown in FIG. 8(d). Here, the registered contents include the information of the sender of the mail and the information of the recipient of the mail (including the password for confidentiality purposes).

However, this PIN number may be registered only in the user management table, and when the mailbox is withdrawn, the user management table may be used to check whether the PIN number matches that of the recipient who accessed the mailbox. ) Email information, registration date and time,
The start address and memory capacity of the memory where this email is stored are registered. The information on the storage location of this memory is File No. (Mail No.) if the memory area is managed by File No.
It's fine just by itself.

Once the email has been added to the confidential box,
In order to notify the recipient of confidential mail No. of the arrival of the confidential mail, the center device creates and sends a CD of a confidential arrival notification to the recipient.

Here, if the transmission of the confidential arrival notification does not end normally, a resending process is performed, and if the resending process does not end normally, a center custody process is performed and the inputting process to the confidential box ends.

Next, if it is a request to withdraw a confidential email, then
) and (d), and check whether they match the number of the called party. If the results match, the email specified by the recipient is pulled out of the confidential box and sent. If the mail is successfully delivered to the recipient, the sent mail is deleted from the confidential mailbox, the registration of the confidential box in the mail management table is deleted, and the process ends. Note that error processing (I) is a process of notifying the recipient of this fact using a CD when the passwords do not match. Error handling (II) is when an email is sent, but it does not end normally. wait.

Next, in the case of a mailbox, as shown in FIG. 12, it is checked whether mail is inserted or withdrawn.

Then, in the case of input, check the recipient from the information on the CD,
Insert the received mail (ND) from the management table in Figure 8(b) into the corresponding mailbox No.
Perform additional registration in the mail management table of the mailbox in C). The contents are the same except for the password. On the other hand, in the case of retrieving mail, the receiving terminal retrieves the mail from the mailbox specified by the CD and sends the mail to the receiving terminal. If the mail is sent successfully, the sent mail N will be displayed in the mail management table of the mailbox in Figure 8 (C).
o from the registration in this table. However, if the email cannot be sent normally, error processing (I
As I[), after removing the error cause and returning to the normal state, the process is terminated and waits for access from the destination terminal again.

Next, in the case of terminal recovery, the center device recognizes that the originating terminal that sent the terminal recovery message has returned to a normal state and is now capable of sending and receiving, and manages the terminal as shown in Figure 8 (a). Make the terminal status in the table good and send a terminal recovery confirmation to this originating terminal. Then, when this terminal is restored, it is checked whether there are any mails that could not be sent and were held at the center due to the terminal being down, from the received information in the center-held mail management table in FIG. 8(e). If there is a corresponding e-mail, the e-mail is sent to that terminal. However, if there is no corresponding email, the process ends.

In the case of the center custody mail service, the center custody mail specified by the information on the CD is searched from the mail information in the center custody mail management table in FIG. Next, check the mail service contents of this mail using the information on the CD, and if it is a withdrawal request for this mail, delete the registration of the mail from the center's mail management table. Send to terminal. However, if it is a distribution request, it goes to FIG. 10, if it is a confidential request, it goes to FIG. 11, and if it is a mailbox request, it goes to FIG. 12, and each service is executed. On the other hand, if there is no email, error handling (IV
), the originating terminal is notified that the specified mail entrusted to the center was not found.

In the case of an inquiry, as shown in FIG. 15, the type of inquiry is checked based on the information on the CD, and the respective processing is executed. When inquiring about the mailbox, please refer to Figure 8 (
The specified mailbox number using the mailbox management table in C).

Select the emails, make a list and send it to the terminal. Next, in the case of inquiries regarding the confidential box, see Figure 8(d).
Using the confidential box management table shown in , the mails in the designated confidential box number are selected and sent as a list to the terminal. In addition, in the case of a communication history inquiry, although a table is not prepared in this embodiment, the communication history of the specified terminal, sender, or recipient is selected from the communication history management table, and sent as a list to the terminal. .

In the case of center custody inquiries, all kinds of emails and notifications are included, so check whether those types are specified or not, and if they are not specified, use the center custody email management table in Figure 8 (e). , sends a list of all emails and notifications addressed to a specified device or person to that device. However, if there is a designation and it is ready immediately, a list of mails will be sent to the designated terminal or individual. Similarly, in the case of broadcast notification, delivery confirmation, and confidential arrival notification, a list of emails and notifications to a designated terminal or individual is notified to that terminal. Thereafter, if the transmission is completed normally, the process is terminated, and if it is not completed normally, the error is cleared, and after returning to normal, it waits for access again.

FIG. 16 shows a subroutine for retransmission processing. Retransmission is repeated up to a specified number of times P, and if the transmission is successfully completed within the specified number of times, the routine returns from this routine. However, if the process does not end normally even after reaching the specified number of times, it is checked to see if the terminal is normal but busy or in use, and if it is busy, the routine returns from this routine as well. On the other hand, if the terminal is not in a busy state and cannot be sent due to a failure in the terminal, the terminal status of this terminal in the terminal management table is changed to bad, and the routine returns from this routine.

Next, FIG. 17 shows a subroutine for proxy distribution processing,
If no substitute terminal is specified in the terminal management table described above, the routine returns directly from this routine. However, if the proxy terminal has been registered, the message is sent to the proxy terminal, and when the sending is normally completed, the routine returns from this routine. On the other hand, if the data cannot be sent normally, a subroutine for retransmission processing is called, and when the routine ends normally, the process returns from this routine. However, if the process does not end normally, it is checked whether there is another proxy terminal, and if there is, proxy distribution is executed again towards that terminal, otherwise the routine returns from this routine.

Further, FIG. 18 shows a subroutine for keeping the data at the center.

First, mails and notifications that could not be sent during resending processing or proxy delivery processing are placed in the center storage box.
The mail is additionally registered in the center storage management table shown in FIG. 8(e).

Next, in order to notify the email sender that this email has been retained by the center, send a notification to the center that it has been retained by the center.
D, and send this CD to the e-mail sender.

When the sending is completed normally, the routine returns from this routine. However, if it does not end normally, retransmission processing is executed, and the above-mentioned processing is executed depending on the result.

Next, the processing procedure of the mail communication terminal in this embodiment will be explained below with reference to the flowchart shown in FIG.

First, when the terminal is powered on, it performs a self-diagnosis and a line connection check, and if it is not in a communicable state due to the occurrence of a failure or the like, it executes error processing (Vl). This process is
Parameter settings, connection settings, etc. are checked, and if a mistake is found and a recovery is possible, the system transitions to a state in which communication is possible. However, if the situation is not met, that is, if there is no prospect of recovery, the power supply is turned OFF, and the faulty part is repaired.

On the other hand, if the terminal is in a communicable state, the terminal sends mail control information to the center device indicating that the terminal is now in a communicable state. In response to this, the center device sends a recovery confirmation to this terminal indicating that it has recognized this terminal recovery, and
When the terminal confirms receipt of this recovery confirmation, normal email service becomes possible.

Next, if the power of the terminal is not turned off, it will be in an idle state waiting for a service request, and if a service request (for example, a mail service request from a sender or a mail transmission from a center device) occurs, the terminal will be in an idle state waiting for a service request. Execute the mail service process, and if it ends normally, it will return to the idle state. If it does not end normally, it will return to the idle state. If it does not end normally, it will return to the idle state.
). This process performs recovery processing for failures caused by operational errors or minor terminal failures (for example, paper jams for fax machines, memory capacity overflow for data terminals), etc., and when recovery occurs, sends a terminal recovery message to the center device. . However, if it does not return, the process ends as described above.

As explained above, with the conventional center storage function, when a mail communication terminal that was down is back up, it sends out a terminal recovery message, and the center device can receive and recognize this message, so that it can be sent to that terminal. You can directly send mail that has been received at the center. As a result, center-received mail can be efficiently transmitted to the other party's terminal, and the memory of the center device can be used effectively accordingly.

Furthermore, since the mail can be delivered to the recipient immediately after the communication-disabled terminal is restored, the time required to deliver the mail can be shortened.

Furthermore, since the terminal notifies the user that the message has been restored, the center device has the effect of improving mail service without having to perform unnecessary retransmission processing.

Furthermore, according to this embodiment, when a terminal that has been in a communication-disabled state returns, the center device updates a table that manages the communication state of that terminal, thereby making it possible to reliably deliver mail.

[Effects of the Invention] As described above, according to the present invention, after a communication-disabled terminal is restored, center-retained mail addressed to the terminal can be directly delivered to the restored terminal.

Furthermore, when delivery failure occurs during communication between the center device and the terminal, updating the management table based on this information has the effect of improving the reliability of the mail system.

[Brief explanation of drawings]

Figure 1 is a system configuration diagram in this embodiment, Figure 2 is a diagram showing the configuration of a mail communication terminal in this embodiment, Figure 3 is a diagram showing the contents of a control document, and Figure 4 is a diagram showing a data communication format. Figure 5 is a sequence diagram showing the communication procedure in the network, Figure 6 is a sequence diagram showing the communication procedure in instant delivery, Figure 7 is a sequence diagram showing the communication procedure in the mailbox, and Figure 8 ( a) to (e) are diagrams showing various management tables, FIGS. 9 to 18 are flowcharts showing the processing procedure of the center device in this embodiment, and FIG. 19 is a diagram showing the processing procedure of the mail communication terminal in this embodiment. FIG. In the figure, 1 to 4... Mail communication terminal, 5... Center device, 6... Network, 7... Central processing unit, 8
...Main storage device, 9...Mass storage device, 10...
・Program storage device, 11... Peripheral device, 12...
・It is a communication control device.

Claims (5)

[Claims] (1) In an e-mail system consisting of a plurality of e-mail communication terminals and a center device having an e-mail storage and exchange function, a means for storing e-mails sent to a terminal and storing them as e-mails when the terminal that should receive e-mails cannot receive the e-mails; An electronic mail system characterized by having means for searching for retained mail when receiving notification of recovery from the terminal, and means for delivering the retained mail to the terminal when the retained mail is found as a result of the search. (2) The center device is characterized by having means for accumulating status information of mail communication terminals, and means for determining, when a contact is received from a mail communication terminal that could not be delivered, that this is a recovery contact. The e-mail system according to claim 1. (3) The e-mail system according to claim 1, wherein the distribution is performed based on a request from a sending terminal. (4) In an e-mail system consisting of a plurality of e-mail communication terminals and a center device having an e-mail storage and forwarding function, the center device stores a management table for managing the communication enabled/disabled status of the e-mail terminal devices, and and means for updating the table based on the information. (5) When a communication failure occurs between the center device and a mail communication terminal, the management table is updated by the mail communication terminal, and when the communication failure state is restored, it is updated by the recovered terminal. 5. The e-mail system according to claim 4, characterized in that: