JP4702393B2 - Gateway device - Google Patents

Description

  The present invention receives an e-mail addressed to a client device from a mail server device, and distributes the received e-mail to the client device in response to a mail reception request command from the client device, while an e-mail from the client device. The present invention relates to a gateway device that transfers a message to a mail server device.

  Since electronic mail has advantages such as convenience and quickness, electronic data such as text data and image data is often transmitted and received using electronic mail in the field of business. However, since the electronic mail is transmitted through an unspecified communication path, there is a possibility that the electronic mail is wiretapped, falsified, and impersonated during the transmission. In order to solve such security problems, e-mail encryption according to the prior art in which e-mail is encrypted using a public key encryption method such as S / MIME (Secure / Multipurpose Internet Mail Extensions) A system has been proposed.

  For example, according to the related art, a plain text email received from each client device is encrypted and transferred to a mail server device, and an encrypted email received from the mail server device is decrypted into a plain text email and distributed to each client device. A gateway device is known. By using such a gateway device, it is possible to improve the safety of sending and receiving electronic mail.

  In Patent Literatures 1 to 4, a device according to the prior art for receiving an electronic mail from a mail server device is disclosed.

Japanese Patent Application Laid-Open No. 11-212893. JP-A-11-238023. Japanese Patent Laid-Open No. 10-75260. Japanese Patent Application Laid-Open No. 2002-229911.

  In the gateway device according to the related art, the compact flash (registered trademark) until the transfer processing for transferring the e-mail received from the client device to the mail server device or the printing processing for sending the e-mail to the printer for printing is completed. Some of them are stored in a removable non-volatile memory. Furthermore, in the gateway device according to the prior art, until the plain text email obtained by decrypting the encrypted email received from the mail server device is transmitted to the client device in response to the reception request command from the client device, Store in the non-volatile memory. Therefore, there is a possibility that the content of the electronic mail in the nonvolatile memory is stolen by removing the nonvolatile memory.

  An object of the present invention is to solve the above-described problems and provide a gateway device capable of improving the safety of transmission / reception of electronic mail as compared with the prior art.

A gateway device according to a first aspect of the present invention is a first storage means for storing plain text e-mail received from a client device;
In a gateway device comprising control means for encrypting the stored plaintext e-mail and transferring it to a mail server device,
Non-volatile second storage means for storing a received mail management table including a relationship between the plain text e-mail and a transfer processing result code indicating whether or not the plain text e-mail has been transferred to the mail server device,
The first storage means is a volatile storage means,
The control means refers to the received mail management table to search for a plain text email that has not been transferred to the mail server device based on the transfer processing result code, and the searched plain text email is the mail server. An error notification mail for notifying that the message has not been transferred to the apparatus is created and distributed to the client apparatus that is the transmission source of the retrieved plain text electronic mail.

In the gateway device, the second storage means further stores a mail header file including a header portion of the plain text email,
The received mail management table includes a relationship between the plaintext e-mail, the mail header file, and a transfer processing result code indicating whether or not the plaintext e-mail has been transferred to the mail server device,
The control means creates the error notification mail including the contents of the mail header file related to the searched plain text electronic mail.

  In the gateway apparatus, the control means stores the error notification mail in the second storage means.

A gateway device according to a second aspect of the present invention is a storage means for storing an e-mail addressed to a client device;
The encrypted electronic mail sent from the mail server device and addressed to the client device is stored in the storage means, the stored encrypted electronic mail is decrypted into plain text electronic mail and stored in the storage means, and the client device In response to the mail reception request command from the gateway device comprising the control means for delivering the plain text email to the client device,
The storage means is a volatile storage means,
The control means distributes the plain text email to the client device in response to the mail reception request command, and then requests an electronic device requesting deletion of the encrypted email corresponding to the delivered plain text email. A mail deletion command is transmitted to the mail server device.

A gateway device according to a third aspect of the present invention is a first storage means for storing plain text e-mail received from a client device;
In a gateway device comprising control means for encrypting the stored plaintext e-mail and transferring it to a mail server device,
A second storage means for storing a received mail management table including a relationship between the plaintext e-mail and a transfer processing result code indicating whether or not the plaintext e-mail has been transferred to the mail server device;
The control means refers to the received mail management table to search for a plain text email that has not been transferred to the mail server device based on the transfer processing result code, and the searched plain text email is the mail server. An error notification mail for notifying that the message has not been transferred to the apparatus is created and distributed to the client apparatus that is the transmission source of the retrieved plain text electronic mail.

A gateway device according to a fourth aspect of the present invention is a storage device for storing an electronic mail addressed to a client device
The encrypted electronic mail sent from the mail server device and addressed to the client device is stored in the storage means, the stored encrypted electronic mail is decrypted into plain text electronic mail and stored in the storage means, and the client device In response to the mail reception request command from the gateway device comprising the control means for delivering the plain text email to the client device,
The control means distributes the plain text email to the client device in response to the mail reception request command, and then requests an electronic device requesting deletion of the encrypted email corresponding to the delivered plain text email. A mail deletion command is transmitted to the mail server device.

  According to the gateway device of the first invention, the control means stores the plain text email received from the client device in the volatile first storage means, and the plain text email and the plain text email are stored in the mail server. Since the received mail management table including the relationship with the transfer processing result code indicating whether or not it has been transferred to the apparatus is stored in the non-volatile second storage means, the safety of sending and receiving e-mail compared to the prior art Can be improved. Further, the control means refers to the received mail management table to search for a plain text email that has not been transferred to the mail server device based on the transfer processing result code, and the searched plain text email is stored in the mail server device. Since an error notification mail for notifying that it has not been forwarded is created and distributed to the client device that is the transmission source of the retrieved plain text email, the gateway device is turned off and stored in the first storage means Even if the plaintext e-mail is deleted, the client device that is the transmission source of the erased plaintext e-mail can retransmit the plaintext e-mail.

  Further, according to the gateway device of the second invention, the control means stores the plain text e-mail decrypted from the encrypted e-mail addressed to the client apparatus transmitted from the mail server apparatus in the volatile storage means. Compared with the prior art, the safety of sending and receiving e-mail can be improved. Furthermore, the control means transmits an e-mail deletion command requesting to delete the encrypted e-mail corresponding to the distributed plain e-mail to the mail server apparatus after distributing the plain e-mail to the client apparatus. To do. Therefore, even if the gateway device is turned off and the plain text email is deleted before the plain text email is delivered to the client device, the erased plain text electronic device is turned on when the gateway device is next turned on. An encrypted electronic mail corresponding to the mail can be received again from the client device.

  Further, according to the gateway device according to the third invention, the control means refers to the received mail management table and searches for a plain text email that has not been transferred to the mail server device based on the transfer processing result code, An error notification mail for notifying that the searched plain text email has not been transferred to the mail server device is created and distributed to the client device that is the transmission source of the searched plain text email. Even if the plain text e-mail stored in the first storage unit is erased, the client device that is the transmission source of the erased plain text e-mail can retransmit the plain text e-mail.

  Still further, according to the gateway device of the fourth invention, the control means requests that the encrypted email corresponding to the delivered plaintext email be deleted after delivering the plaintext email to the client device. An email deletion command is transmitted to the mail server device. Therefore, even if the gateway device is turned off and the plain text email is deleted before the plain text email is delivered to the client device, the erased plain text electronic device is turned on when the gateway device is next turned on. An encrypted electronic mail corresponding to the mail can be received again from the client device.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each following embodiment, the same code | symbol is attached | subjected about the same component.

First embodiment.
FIG. 1 shows a local area network (hereinafter referred to as a LAN) including an S / MIME gateway device 20 having a function of transmitting and receiving an electronic mail using S / MIME according to the first embodiment of the present invention. FIG. 2 is a block diagram showing a system configuration.

  The LAN system according to this embodiment includes a plurality of N client personal computers 30-1 to 30-N (hereinafter collectively referred to as reference numeral 30), an S / MIME gateway device 20, a router device 60, A mail server device 40 connected to the Internet 90 is connected via a LAN 70. 2 to 4 are block diagrams showing configurations of the client personal computer 30, the S / MIME gateway device 20, and the mail server device 40 of FIG. 1, respectively. The configurations of the LAN system, client personal computer 30, S / MIME gateway device 20, and mail server device 40 in FIGS. 1 to 4 are applied to the first and second embodiments.

  Each client personal computer 30 is configured to be able to send and receive e-mails encrypted using S / MIME by connecting to the mail server device 40 via the S / MIME gateway device 20 and the router device 60. .

  Here, the S / MIME gateway apparatus 20 encrypts the stored plaintext email and stores the plaintext email received from the client personal computer 30 and SMTP (Simple Mail Transfer Protocol) receiving mailbox 10. In a gateway device including a main control unit 1 for transferring to a server device 40, a mail header file memory 3 for storing a mail header file including a header part of the plain text email, the plain text email, and the mail header file And a flash ROM 2 which is a non-volatile storage means for storing a received mail management table 2t including a relationship with a transfer processing result code indicating whether or not the plain text electronic mail has been transferred to the mail server device 40, SMTP receiving mailbox 10 is The main control unit 1 is transferred to the mail server device 40 based on the transfer processing result code with reference to the received mail management table 2t. The plaintext e-mail that did not exist is searched, an error notification e-mail is generated to notify that the searched plaintext e-mail has not been transferred to the mail server device 40, and the client personal of the sender of the searched plaintext e-mail is created It is characterized by being distributed to the computer 30.

  Further, the main control unit 1 creates an error notification mail including the contents of the mail header file related to the searched plain text electronic mail and stores it in the error notification mail mailbox 4 in the flash ROM 2. Yes.

  Still further, the S / MIME gateway device 20 includes a POP3 (Post Office Protocol Ver. 3) receiving mailbox 8 for storing an electronic mail addressed to the client personal computer 30 and the client personal computer 30 transmitted from the mail server device 40. The encrypted e-mail addressed to the POP3 receiving mail box 8 is stored, the stored encrypted e-mail is decrypted into plain text e-mail and stored in the POP3 receiving mail box 8, and the encrypted personal e-mail from the client personal computer 30 is stored. In response to the mail reception request command of FIG. 2, the POP3 reception mailbox 8 is included in the SRAM 7 which is a volatile storage unit in the gateway apparatus including the main control unit 1 that distributes the plain text electronic mail to the client personal computer 30. This In response to the second mail reception request command, the main control unit 1 distributes the plain text email to the client personal computer 30, and then requests to delete the encrypted email corresponding to the distributed plain text email. The electronic mail deletion command is transmitted to the mail server device 40.

  Distribution of e-mail to each client personal computer 30 by the S / MIME gateway device 20 is performed as follows by POP3 reception processing described later in detail using FIG. 6 and e-mail distribution processing described in detail later using FIG. To be done. The main control unit 1 (see FIG. 3) of the S / MIME gateway apparatus 20 transmits the first mail reception request command to the mail server apparatus 40 at every predetermined time interval, and all of the responses transmitted in response thereto are sent. Encrypted electronic mail with an electronic signature addressed to the client personal computers 30-1 to 30 -N is received from the mail server device 40. Then, decryption processing and electronic signature verification processing are performed on the received encrypted electronic mail with electronic signature, converted into plain text electronic mail, and stored in the POP3 reception mailbox 8 (see FIG. 3). Further, in response to each second mail reception request command from each client personal computer 30-1 to 30-N, the plain text electronic mail stored in the POP3 reception mailbox 8 is transferred to each client personal computer 30-1. Deliver to ~ 30-N. In response to the second mail reception request command, an error notification mail stored in an error notification mail mailbox 4 described later in detail is also distributed to the client personal computer 30.

  In addition, transmission of plain text e-mail from each client personal computer 30 is performed as follows by e-mail transfer processing described later in detail with reference to FIG. First, each client personal computer 30 transmits the created plain text electronic mail to the S / MIME gateway device 20. The S / MIME gateway device 20 stores the plain text e-mail received from each client personal computer 30 in the SMTP receiving mailbox 10 (see FIG. 3). Further, the S / MIME gateway apparatus 20 converts the stored plaintext e-mail into an encrypted e-mail with an electronic signature by performing an electronic signature process and an encryption process using the S / MIME. Then, the S / MIME gateway device 20 transfers the encrypted electronic mail with the electronic signature to the mail server 40 via the router device 60.

  Next, the configuration of the client personal computer 30 will be described with reference to FIG.

  In FIG. 2, a client personal computer 30 is an external terminal device that is a known personal computer, and executes processing such as generation, recording, storage, transmission, and reception of plain text e-mail, image data, and character data. The client personal computer 30 is used as a client device, and transmits the generated plain text electronic mail to the S / MIME gateway device 20. Further, the client personal computer 30 transmits a second mail reception request command for requesting reception of an e-mail to the S / MIME gateway apparatus 20, and is transmitted from the S / MIME gateway apparatus 20 in response thereto. Receive plain text emails. The second mail reception request command is generated at predetermined time intervals or according to a predetermined instruction command for instructing reception of an electronic mail input by the user of the client personal computer 30 via the operation unit 105. .

  The e-mail transmission / reception program of the client personal computer 30 is stored in the hard disk drive 108 of the client personal computer 30 in advance. The e-mail transmission / reception program is a known control program for creating an e-mail and transmitting / receiving an e-mail via the S / MIME gateway apparatus 20.

  The main control unit 101 is specifically composed of a CPU (Central Processing Unit) and is connected to the following hardware units via the bus 113 to control them and execute various software functions. . The display unit 104 is a display device such as a liquid crystal display device (LCD (Liquid Crystal Display)) or a CRT (Cathode Ray Tube) display, and displays the operating state of the client personal computer 30, e-mail to be sent and received The displayed e-mail. The operation unit 105 is, for example, a keyboard, and is used for inputting an instruction command for receiving character data and an e-mail.

  A ROM (Read Only Memory) 106 stores various software programs necessary for the operation of the client personal computer 30 and executed by the main control unit 101 in advance. A RAM (Random Access Memory) 107 is composed of SRAM, DRAM (Dynamic RAM), SDRAM (Synchronous DRAM), etc., and is used as a working area of the main control unit 101 to generate temporary data generated when a program is executed. Remember. Further, the hard disk drive 108 is a storage device that incorporates a recording medium, and stores an application program to be executed and an image memory. In the first and second embodiments, the hard disk drive 108 stores the e-mail transmission / reception program of the client personal computer 30 as described above. Further, the LAN interface 112 is connected to the LAN 70 and receives signals and data from the LAN 70, and transmits signals and data to the LAN 70 to execute interface processing related to LAN communication such as signal conversion and protocol conversion. .

  Next, the configuration of the S / MIME gateway apparatus 20 will be described with reference to FIG.

  The S / MIME gateway device 20 has an e-mail transmission / reception function for transmitting / receiving e-mails using S / MIME. In the e-mail transmission / reception function of the S / MIME gateway device 20, plain text e-mail received from each client personal computer 30 is stored in the SMTP reception mailbox 10, and electronic signature processing and encryption processing are performed by software according to S / MIME. Is transferred to the mail server device 40. Further, as will be described in detail later, in the S / MIME gateway apparatus 20, a first mail reception request command for requesting transmission of e-mails addressed to all client personal computers 30 is generated at predetermined time intervals. It is transmitted to the mail server device 40. In response to this, the encrypted electronic mail with electronic signature received from the mail server device 40 is decrypted and converted to plain text electronic mail by software according to S / MIME and then received as POP3. Stored in the mailbox 8. Further, as will be described later, the electronic mail stored in the mailbox 8 is delivered to each client personal computer 30 in response to a second mail reception request command from each client personal computer 30. That is, the S / MIME gateway device 20 functions as an SMTP server device and a POP3 server device for each client personal computer 30 and also functions as an SMTP client device and a POP3 client device for the mail server device 40.

  In the S / MIME gateway device 20, the main control unit 1 is specifically composed of a CPU and is connected to the following hardware units via the bus 13 to control them, and various software described later. Perform the function. The ROM 6 stores various software programs that are necessary for the operation of the S / MIME gateway device 20 and executed by the main control unit 1 in advance.

  The hard disk drive 9 is a storage device that contains a recording medium, and stores various data and programs. In this embodiment, at least the POP3 reception process (FIG. 6) of the S / MIME gateway device 20 and electronic mail Each program includes a delivery process (FIG. 7), an e-mail transfer process (FIG. 8), and an error notification mail generation process (FIG. 9). The LAN interface 12 is connected to the LAN 70 and receives signals and data from the LAN 70, and transmits signals and data to the LAN 70 to execute interface processing related to LAN communication such as signal conversion and protocol conversion. . Further, when a predetermined time-up time (for example, 10 minutes) has elapsed since the timer circuit 5 was reset, the timer circuit 5 transmits a control signal indicating the time-up to the main control unit 1. Furthermore, the printer 11 is a printer apparatus such as an electrophotographic system, and prints an error notification mail in an error notification mail mailbox or records character data.

  Furthermore, the SRAM 7 which is a volatile memory is used as a working area of the main control unit 1 and stores temporary data generated when the program is executed. In the first and second embodiments, the SRAM 7 is received from the POP3 receiving mailbox 8 for storing the e-mail addressed to the client personal computer 30 received from the mail server device 40 and each client personal computer 30. And an SMTP receiving mailbox 10 for storing e-mails. If the power is cut off due to a power failure, apparatus movement, or the like, the e-mail stored in the POP3 receiving mailbox 8 and the SMTP receiving mailbox 10 is deleted.

  The flash ROM 2 which is a non-volatile memory such as CompactFlash (registered trademark), for example, has a mail header file memory 3 for storing a mail header file including a header portion of each electronic mail received from each client personal computer 30. FIG. 9 includes an error notification mail mailbox 4 that stores an error notification mail addressed to the client personal computer 30 that is generated by an error notification mail generation process that will be described in detail later with reference to FIG. Further, the flash ROM 2 stores a received mail management table 2t, which will be described in detail later with reference to FIG. The mail header file in the mail header file memory 3, the error notification mail in the error notification mail mailbox 4, and the received mail management table 2t have been powered off due to power failure, device movement, etc. Even if the contents are not lost.

  FIG. 5 is a diagram showing an example of items and contents of received mail management data written in each record of the received mail management table 2t of FIG. The received mail management table 2t is used to manage each email received from the client personal computer 30 and the mail server device 40 as a queue, and includes a plurality of records corresponding to each email. As shown in FIG. 5, the received mail management data written in each record includes a management number having an integer value, a processing status of the record, a session start time related to the record, and an e-mail related to the record. A reception means code indicating whether the e-mail has been received by POP3 or SMTP, a transfer process result code indicating a transfer process result of the received e-mail to the mail server device 40, and the e-mail It includes the user ID of the sender or destination user, the message ID of the email, and the file path associated with the email. Here, the processing status includes (a) a status in which the record is empty, (b) a status in which the record is reserved, (c) a status in which an electronic mail related to the record has been received, and (d) It includes a status that the electronic mail related to the record is being processed, and (d) a processing status that the processing of the electronic mail related to the record is completed. In the first embodiment, the transfer processing result code is used to determine whether the electronic signature processing and encryption processing (step S55 in FIG. 8) for each electronic mail from the client personal computer 30 has been completed normally (encryption processing abnormality). End), whether or not the transmission process of the e-mail to the mail server device 40 (S58 in FIG. 8) has ended normally (abnormal end of the transmission process), and all of the electronic signature process, the encryption process, and the transmission process Each transfer processing result code indicating whether or not the electronic mail has been normally transferred and transferred to the mail server device 40 (transfer processing complete or transfer processing incomplete) is included. Furthermore, the file path indicates the path of a header file that stores the header part of the electronic mail.

  Next, the configuration of the mail server device 40 will be described with reference to FIG.

  In FIG. 4, a mail server device 40 is a well-known mail server device, and executes e-mail transmission / reception processing. The mail server device 40 transmits the encrypted electronic mail with the electronic signature from the S / MIME gateway device 20 to the destination mail server device (not shown) via the Internet 90. Further, the mail server device 40 stores the encrypted electronic mail with the electronic signature from the mail server device (not shown) of the transmission source in the mail box 402. Further, in response to the first mail reception request command from the S / MIME gateway device 40, the e-mail addressed to all the client personal computers 30 is transmitted to the S / MIME gateway device 40. At this time, the mail server device 40 holds the electronic mail transmitted to the S / MIME gateway device 40 without deleting it from the mail box 402. Further, in response to an e-mail deletion command for requesting deletion of a predetermined e-mail from the S / MIME gateway device 40, the predetermined e-mail is deleted from the mailbox 402. The e-mail transmission / reception program of the mail server device 40 is stored in the hard disk drive 408 in advance. The electronic mail transmission / reception program is a known control program for transmitting / receiving an encrypted electronic mail with an electronic signature to / from the S / MIME gateway apparatus 20.

  The main control unit 101 is specifically composed of a CPU and is connected to the following hardware units via the bus 413 to control them and execute various software functions. The display unit 104 is a display device such as a liquid crystal display device (LCD) or a CRT display, and displays the operation state of the mail server device 40. The operation unit 405 is, for example, a keyboard, and is used for inputting character data and instruction commands.

  The ROM 406 stores various software programs that are necessary for the operation of the mail server device 40 and executed by the main control unit 401 in advance. The RAM 407 is composed of SRAM, DRAM, SDRAM, etc., and is used as a working area for the main control unit 401 to store temporary data generated when the program is executed. Further, the hard disk drive 408 is a storage device that incorporates a recording medium, and stores an application program to be executed and an image memory. In the first and second embodiments, the hard disk drive 408 stores an e-mail transmission / reception program as described above. The hard disk drive 408 includes a mail box 402. Note that the contents of the data in the hard disk drive 408 are not lost even when the power is cut off due to a power failure, movement of the device, or the like. Further, the interface 414 is connected to the Internet 90 and receives signals and data from the Internet 90, while transmitting signals and data to the Internet 90 to perform interface processing related to Internet communication such as signal conversion and protocol conversion. Execute. The LAN interface 412 is connected to the LAN 70 and receives signals and data from the LAN 70, and transmits signals and data to the LAN 70 to execute interface processing related to LAN communication such as signal conversion and protocol conversion. .

  FIG. 6 is a flowchart showing the POP3 reception process according to the first embodiment, which is executed by the main control unit 1 of the S / MIME gateway apparatus 20 of FIG.

  In FIG. 6, first, in step S1, it is determined whether or not the power of the S / MIME gateway device 20 is turned on. If NO, the process of step S1 is repeated, and if YES, the process proceeds to step S2. In step S <b> 2, the first mail reception request command is transmitted to the mail server device 40. In response to the first mail reception request command, the mail server device 40 transmits the encrypted electronic mail with the electronic signature addressed to the client personal computer 30 stored in the mail box 402 to the S / MIME gateway device 20, The encrypted electronic mail with electronic signature is stored in the mail box 402. Next, in step S3, the encrypted electronic mail with electronic signature addressed to the client personal computer 30 is received from the mail server device 40, and the received encrypted electronic mail with electronic signature is decrypted and verified. And converted into plain text e-mail, and then stored in the POP3 receiving mailbox 8. Next, in step S4, the timer circuit 5 is reset, and the process proceeds to step S5. In step S5, it is determined whether or not a predetermined time-up time has elapsed and a control signal indicating the time-up has been received from the timer circuit 5. If YES, the process returns to step S2, while if NO, The process of step S5 is repeated.

  Therefore, the main control unit 1 executes the POP3 reception process of FIG. 6 so that the mail server device 40 sends the client personal computer when the power of the S / MIME gateway device 20 is turned on and every predetermined time-up time. An e-mail addressed to the computer 30 is received.

  FIG. 7 is a flowchart showing an e-mail delivery process according to the first embodiment, which is executed by the main control unit 1 of the S / MIME gateway apparatus 20 of FIG.

  In FIG. 7, first, in step S30, it is determined whether or not the second mail reception request command has been received from the specific client personal computer 30. If NO, the process of step S30 is repeated, whereas if YES, Proceed to step S31. In step S31, it is determined whether or not the plain text e-mail addressed to the client personal computer 30 that has transmitted the second mail reception request command is in the POP3 reception mailbox 8. If NO, the process proceeds to step S34, but YES. If so, the process proceeds to step S32. In step S32, the plain text electronic mail addressed to the client personal computer 30 that has transmitted the second mail reception request command is distributed to the client personal computer 30, and the process proceeds to step S33. In step S33, an e-mail delete command for requesting deletion of the encrypted electronic mail with electronic signature corresponding to the plain text e-mail distributed to the client personal computer 30 from the mailbox 402 of the mail server apparatus 40 is sent to the mail server apparatus. The process proceeds to step S34. The mail server device 40 deletes the encryption with the electronic signature corresponding to the electronic mail distributed to the client personal computer 30 from the mail box 402 in response to the electronic mail deletion command.

  Next, in step S34, it is determined whether or not the error notification mail addressed to the client personal computer 30 that has transmitted the second mail reception request command is in the error notification mail mailbox 4. If NO, the process returns to step S30. On the other hand, if YES, the process proceeds to step S35. In step S35, the error notification mail addressed to the client personal computer 30 that has transmitted the second mail reception request command is distributed to the client personal computer 30, and the process returns to step S30. The method of creating the error notification mail stored in the error notification mail mailbox 4 will be described later in detail with reference to FIG.

  FIG. 8 is a flowchart showing an e-mail transfer process according to the first embodiment, which is executed by the main control unit 1 of the S / MIME gateway apparatus 20 of FIG.

  In FIG. 8, first, in step S51, it is determined whether or not a plain text e-mail has been received from the client personal computer 30. If NO, the process of step S51 is repeated. If YES, the process proceeds to step S52. The plain text e-mail is stored in the SMTP receiving mailbox 10. Next, in step S <b> 53, a header file including the content of the header part of the received plain text electronic mail is generated and stored in the mail header file memory 3. Here, the header part of the plain text e-mail contains the e-mail address, the creation time, the subject (Subject), the message ID (Message-Id), and the MIME version information (MIME-Version) of the e-mail. Including. Furthermore, in step S54, one record is secured in the received mail management table 2t, and the secured record includes the path of the created mail header file, the transfer process result code indicating that transfer process is incomplete, and SMTP reception. The received mail management data including the receiving means code indicating this is written. Next, in step S55, the stored plain text electronic mail is subjected to electronic signature processing and encryption processing, converted into encrypted electronic mail with electronic signature, and then the process proceeds to step S55.

  In step S56, it is determined whether or not the electronic signature process and the encryption process in step S55 have been normally completed. If YES, the process proceeds to step S58. If NO, the process proceeds to step S57. For example, when the certificate is not registered, the electronic signature process and the encryption process end abnormally. In step S57, in the secured record of the received mail management table 2t, the transfer process result code indicating that the transfer process has not been completed is written over the transfer process result code indicating that transfer process has not been completed, and the process returns to step S51. .

  In step S58, transmission processing for transmitting the stored encrypted electronic mail with electronic signature to the mail server device 40 is performed. In step S59, it is determined whether or not the transmission process has been normally completed. If YES, the transfer process result code indicating the completion of the transfer process is overwritten with the transfer process result code indicating that the transfer process has not been completed in step S61. And return to step S51. On the other hand, if NO in step S59, in step S60, the transfer process result code indicating incomplete transfer process is overwritten with the transfer process result code indicating abnormal end of transmission process, and the process returns to step S51. For example, the transmission process ends abnormally when the mail server device 40 is out of order or when the transmission path between the S / MIME gateway device 20 and the mail server device 40 is unavailable.

  By the e-mail transfer process of FIG. 8, the relationship between each e-mail from the client personal computer 30, the mail header file path of the e-mail, and the transfer process result code is shown in each record of the received mail management table 2t. Written. Here, as described above, the transfer processing result code indicates whether or not the electronic signature processing and encryption processing (step S55 in FIG. 8) for each electronic mail from the client personal computer 30 has been completed normally (encryption processing abnormal termination). ), Whether or not the transmission process of the e-mail to the mail server device 40 (S58 in FIG. 8) ended normally (transmission process abnormal end), and all of the electronic signature process, encryption process and transmission process are normal Each transfer processing result code indicating whether or not the e-mail has been transferred to the mail server device 40 after completion (transfer processing completed or transfer processing incomplete) is included.

  FIG. 9 is a flowchart showing an error notification mail generation process according to the first embodiment, which is executed by the main control unit 1 of the S / MIME gateway apparatus 20 of FIG. The error notification mail generation process of FIG. 9 is executed when the power of the S / MIME gateway apparatus 20 is turned on and at other predetermined timing.

  In FIG. 9, first, in step S80, the first record of the received mail management table 2t is read. In step S81, it is determined whether or not the receiving means code related to the read record indicates SMTP reception. Is done. If NO in step S81, the process proceeds to step S83. If NO, the process proceeds to step S82. In step S82, it is determined whether or not the transfer process result code related to the read record indicates that the transfer process is successful. If YES in step S82, the process proceeds to step S83. If NO, the process proceeds to step S85. In step S83, it is determined whether or not the read record is the last record. If YES, the error notification mail generation process is terminated. If NO, the received mail management table 2t is checked in step S84. The next record is read, and the process returns to step S81.

  In step S85, it is determined whether or not the transfer processing result code relating to the read record indicates that the encryption processing has ended abnormally. If YES, the process proceeds to step S86. If NO, the process proceeds to step S88. . Next, in step S86, the mail header file having the file path related to the read record is read from the mail header file memory 3. In addition, an error notification mail is sent to the sender of the email related to the read record, including the contents of the read mail header file, and an error notification mail is sent to notify the abnormal end of the encryption process. Store in box 4. Here, the email address of the sender of the email related to the read record is read from the mail header file. Next, the process proceeds to step S87.

  In step S88, it is determined whether or not the transfer process result code related to the read record indicates abnormal termination of the transmission process. If YES, the process proceeds to step S89. If NO, the process proceeds to step S90. Next, in step S89, the mail header file having the file path related to the read record is read from the mail header file memory 3. In addition, an error notification mail is sent to the sender of the email related to the read record, including the contents of the read mail header file, and an error notification mail mailbox is sent to notify the abnormal end of transmission processing. 4 is stored. Next, the process proceeds to step S87.

  In step S90, the mail header file having the file path related to the read record is read from the mail header file memory 3. In addition, an error notification email is sent to the sender of the email related to the read record, including the contents of the read email header file. Store in box 4. Next, the process proceeds to step S87.

  The error notification mail generated in steps S86, S89 and S90 is stored in the error notification mail mailbox 4, and is transmitted to the printer and printed in step S87. The error notification mail stored in the error notification mail mailbox 4 is distributed to the client personal computer 30 by the electronic mail distribution processing (see steps S34 and S35) of FIG.

  10 receives the error notification mail for notifying the abnormal end of the encryption process generated in step S86 of FIG. 9 by the client personal computer 30 of FIG. It is a front view which shows the example of a display 601 displayed on the display part 104 using. In the display example 601 of FIG. 10, an error notification mail 602 for notifying the abnormal end of the encryption process is displayed. The error notification mail 602 includes a first part 603 including information on details of an error generated based on the transfer processing result code indicating the abnormal end of the encryption process, and the header of the e-mail in which the abnormal end of the encryption process has occurred. A second portion 604 containing content. Here, the second part 604 includes the email address of the sender of the email where the abnormal end of the encryption process has occurred (in the example of FIG. 10, user5@aaa.bb) and the destination email address. (User1@aaa.bb in the example of FIG. 10), creation date and time (in the example of FIG. 10, it is 8:40:26 on December 21, 2007, Japan time), and subject (example of FIG. 10) Is not specified) and a message ID (20071221084006ADA8.USER5@aaa.bb in FIG. 10).

  Also, FIG. 11 shows an error notification mail for notifying the abnormal end of the transmission process generated in step S89 of FIG. 9 by the client personal computer 30 of FIG. It is a front view which shows the example of a display 701 displayed on the display part 104 using FIG. In the display example 701 of FIG. 11, an error notification mail 702 for notifying the abnormal end of transmission processing is displayed. The error notification mail 702 includes a first part 703 including information on details of an error generated based on a transfer processing result code indicating abnormal termination of transmission processing, and the contents of the header of the email in which the abnormal termination of transmission processing has occurred. Including a second portion 704. Here, the second portion 704 includes an e-mail address of the sender of the e-mail in which the abnormal end of the transmission process has occurred (in the example of FIG. 11, user1@aaa.bb), and a destination e-mail address. (In the example of FIG. 11, user1@aaa.bb, user2@aaa.bb, user3@aaa.bb, and user4@aaa.bb.) And the creation date and time (in the example of FIG. May 20, 15:56:26) and subject (in the example of FIG. 11, test (2007/12/20 15.55.45) [1]) message ID (in the example of FIG. 11, 20071220155545.6313 .USER1 @ aaa.bb.)

  As described above in detail, according to the S / MIME gateway device 20 according to the present embodiment, the received electronic mails received from the mail server device 40 and the client personal computer 30 are respectively stored in the SRAM 7 which is a volatile memory. They are stored in the POP3 reception mailbox 8 and the SMTP reception mailbox 10. Therefore, in comparison with the gateway device according to the related art that stores the received electronic mail received from the mail server device 40 and the client personal computer 30 in a removable nonvolatile memory such as CompactFlash (registered trademark). The content of the e-mail is not stolen, and there is a specific effect that the processing speed is high.

  Further, according to the S / MIME gateway device 20 according to the present embodiment, after the electronic mail received from the mail server device 40 is distributed to the client personal computer 30 (step S32 in FIG. 7), the electronic mail is sent to the mail server. An email deletion command to be deleted from the mail box 402 of the device 40 is transmitted to the mail server device 40. Therefore, the e-mail addressed to the client personal computer 30 is received from the mail server device 40 and stored in the POP3 receiving mailbox 8 until it is delivered to the client personal computer 30. Even if the e-mail in the POP3 reception mailbox 8 is deleted after the power is turned off, the deleted e-mail is re-received from the mail server apparatus 40 after the power of the S / MIME gateway apparatus 20 is turned on again. it can.

  Further, according to the S / MIME gateway apparatus 20 according to the present embodiment, the electronic mail from the client personal computer 30 is stored in the SMTP reception mailbox 10 of the SRAM 7 which is a volatile memory (step S52 in FIG. 8). Then, a header file including the header part of the electronic mail is generated and stored in the mail header file memory 3 of the flash ROM 2 which is a nonvolatile memory (step S53 in FIG. 8). Furthermore, the relationship between each e-mail from the client personal computer 30 and the path of the mail header file of the e-mail, and whether or not the electronic signature process and encryption process (step S55 in FIG. 8) for the e-mail have ended normally. Whether or not the transmission processing of the electronic mail to the mail server device 40 (S58 in FIG. 8) has been normally completed, all of the electronic signature processing, encryption processing and transmission processing have been normally completed, and the electronic mail is mailed. A received mail management table 2t including a plurality of records each storing a transfer processing result code indicating whether or not transfer to the server device 40 has been completed is stored in the flash ROM 2. The S / MIME gateway apparatus 20 refers to the received mail management table 2t (step S80 in FIG. 9), and searches for e-mails that have not been transferred to the mail server apparatus 40 among e-mails received from the client personal computer 30. (Step S82 in FIG. 9), an error notification mail is created based on the transfer processing result code relating to the untransferred e-mail and the contents of the mail header file, and stored in the error notification mail mailbox 4 (FIG. 9). 9 and steps S86, S89, and S90), the data is transmitted to the printer 11 and printed (step S87 in FIG. 9). Therefore, S / MIME is stored between the time when the electronic mail from the client personal computer 30 is stored in the SMTP receiving mailbox 10 (step S53 in FIG. 8) and transferred to the mail server device 40 (step S58 in FIG. 8). Even when the gateway device 20 is turned off and the e-mail in the SMTP receiving mailbox 10 is deleted and the transfer is not completed, the received mail management table 2t in the flash ROM 2 and the mail header file memory 3 Based on the mail header file, an error notification mail for notifying the incomplete transfer, the abnormal end of the encryption process, or the abnormal end of the transmission process is created, sent to the printer 11, printed, and the deleted e-mail Can be distributed to the client personal computer 30 of the transmission source.

  Further, the electronic mail received from the mail server device 40 and the client personal computer 30 is stored in the SRAM 7 which is a volatile memory, and the mail header file, the error notification mail and the received mail management table 2t are stored in the flash ROM 2 which is a nonvolatile memory. Since it is stored, the safety of sending and receiving e-mail can be improved compared to the prior art.

Second embodiment.
In the second embodiment according to the present invention, the hard disk drive 9 of the S / MIME gateway apparatus 20 performs the e-mail transfer process in FIG. 12 and the error notification mail generation process in FIG. 13 as compared with the first embodiment. The program is stored. Further, the transfer process result code written in each record of the received mail management table 2t is whether or not the transfer process for transferring the e-mail from the client personal computer 30 to the mail server device 40 has been completed (transfer process completed). A transfer processing result code indicating whether or not (see FIG. 5). Other configurations are the same as those of the first embodiment.

  FIG. 12 is a flowchart showing an e-mail transfer process according to the second embodiment, which is executed by the main control unit 1 of the S / MIME gateway apparatus 20 of FIG. The electronic mail transfer process of FIG. 12 differs from the electronic mail transfer process of FIG. 8 only in the process when NO in step S56 and the process when NO in step S59. Specifically, when it is determined in step S56 that the electronic signature process and the encryption process have not been completed normally, the process proceeds to step S100, and the read record is the same as the process in step S86 of FIG. The mail header file having the file path is read from the mail header file memory 3. In addition, an error notification mail is sent to the sender of the email related to the read record, including the contents of the read mail header file, and an error notification mail is sent to notify the abnormal end of the encryption process. Store in box 4. Next, the process proceeds to step S102.

  If it is determined in step S59 that the transmission process has not been completed normally, the process proceeds to step S101, and the mail header having the file path related to the read record, as in the process of step S89 in FIG. The file is read from the mail header file memory 3. In addition, an error notification mail is sent to the sender of the email related to the read record, including the contents of the read mail header file, and an error notification mail mailbox is sent to notify the abnormal end of transmission processing. 4 is stored. Next, the process proceeds to step S102. In step S102, the generated error notification mail is transmitted to the printer 11 for printing, and the process returns to step S51.

  By the electronic mail transfer process of FIG. 12, the relationship between each electronic mail from the client personal computer 30 and the mail header file of the electronic mail and the electronic mail are transferred to the mail server device 40 in each record of the received mail management table 2t. Each transfer process result code indicating the completion of the transfer process to be performed (transfer process complete) or the transfer process incomplete (transfer process incomplete) is written. Further, when the electronic signature process and the encryption process in step S56 are abnormally terminated, an error notification mail for notifying the abnormal end of the encryption process is created and stored in the error notification mail mailbox 4. When the transmission process in step S59 ends abnormally, an error notification mail notifying the abnormal end of the transmission process is created and stored in the error notification mail mailbox 4.

  FIG. 13 is a flowchart showing an error notification mail generation process according to the second embodiment, which is executed by the main control unit 1 of the S / MIME gateway apparatus 20 of FIG. The error notification mail generation process of FIG. 13 differs from the error notification mail generation process of FIG. 9 only in that it does not include steps S85 to S89, and proceeds to step S90 when NO in step S82.

  According to the S / MIME gateway apparatus 20 according to the present embodiment, the flash ROM 2 stores each electronic mail from the client personal computer 30, the path of the mail header file of the electronic mail, and the electronic mail to the mail server apparatus 40. A received mail management table 2t including a plurality of records each including a relationship with a transfer process result code indicating whether transfer has been completed (transfer process completed or transfer process incomplete) is stored. The S / MIME gateway apparatus 20 refers to the received mail management table 2t (step S80 in FIG. 13) and searches for e-mails that have not been transferred to the mail server apparatus 40 from e-mails received from the client personal computer 30. (Step S82 in FIG. 13), an error notification mail is created based on the transfer processing result code relating to the untransferred e-mail and the contents of the mail header file, and stored in the error notification mail mailbox 4 (FIG. 13). 13 is sent to the printer 11 and printed (step S87 in FIG. 13). Therefore, the S / MIME is stored between the time when the electronic mail from the client personal computer 30 is stored in the SMTP receiving mailbox 10 (step S53 in FIG. 8) and transferred to the mail server device 40 (step S58 in FIG. 12). Even when the gateway device 20 is turned off and the e-mail in the SMTP receiving mailbox 10 is deleted and the transfer is not completed, the received mail management table 2t in the flash ROM 2 and the mail header file memory 3 Based on the mail header file, an error notification mail for notifying the incomplete transfer can be created, transmitted to the printer 11, printed, and distributed to the client personal computer 30 that is the transmission source of the deleted e-mail.

  In the above embodiment, the S / MIME gateway device 20 transmits the error notification mail to the printer 11 and prints it (step S87 in FIGS. 9 and 13 and step S102 in FIG. 12), but the present invention is not limited to this. The S / MIME gateway device 20 may create a report including the content of the error notification mail and transmit the report to the printer 11 for printing.

  The flash ROM 2 stores a received mail management table including the relationship between the plain text e-mail from the client personal computer 30 and the transfer processing result code indicating whether or not the plain text e-mail has been transferred to the mail server device 40. Also good. At this time, the main control unit 1 refers to the received mail management table and searches for the plain text email that has not been transferred to the mail server device 40 based on the transfer processing result code, and the searched plain text electronic An error notification mail notifying that the mail has not been transferred to the mail server device 40 may be created and distributed to the client personal computer 30 that is the transmission source of the searched plain text electronic mail.

  Further, in the above embodiment, the mail header file memory 3, the error notification mail mailbox 4 and the received mail management table 2t are stored in the flash ROM 2, but the present invention is not limited to this, and the mail header file memory 3, error The notification mail mailbox 4 and the received mail management table 2t may be stored in a nonvolatile storage means such as the hard disk drive 9.

  In the above embodiment, the POP reception mailbox 8 and the SMTP reception mailbox 10 are provided in the SRAM 7 which is a volatile storage unit. However, the present invention is not limited to this, and the detection means for detecting that the power of the S / MIME gateway apparatus 20 is turned off and generating a detection signal indicating the detection is output. The POP receiving mailbox 8 and the SMTP receiving mailbox 10 may be provided in the nonvolatile storage means. At this time, when the main control unit 1 detects that the power of the S / MIME gateway apparatus 20 is turned off based on the detection signal, the main control unit 1 stores the POP reception mailbox 8 and the SMTP reception mailbox 10. Each plain text e-mail is deleted by executing predetermined application software or operating a predetermined electronic circuit. Further, in the above embodiment, the mail header file memory 3, the error notification mail mailbox 4, and the received mail management table 2t are provided in the flash ROM 2. However, the present invention is not limited to this, and is provided in a volatile storage means. Also good.

  Furthermore, in the above embodiment, the example of the S / MIME gateway device 20 has been described. However, the present invention is not limited to this, and an e-mail addressed to the client device is received from the mail server device, In response to a mail reception request command, for example, a digital multi-function peripheral, a data communication device, and a server device having a function of delivering received electronic mail to a client device and transferring the email from the client device to a mail server device. The present invention can be applied to communication terminal apparatuses including Internet facsimile apparatuses.

  As described in detail above, according to the gateway device of the first invention, the control means stores the plaintext email received from the client device in the volatile first storage means, and the plaintext email and the Since the received mail management table including the relationship with the transfer processing result code indicating whether or not the plain text e-mail has been transferred to the mail server device is stored in the non-volatile second storage means, compared with the prior art, The safety of sending and receiving e-mail can be improved. Further, the control means refers to the received mail management table to search for a plain text email that has not been transferred to the mail server device based on the transfer processing result code, and the searched plain text email is stored in the mail server device. Since an error notification mail for notifying that it has not been forwarded is created and distributed to the client device that is the transmission source of the retrieved plain text email, the gateway device is turned off and stored in the first storage means Even if the plaintext e-mail is deleted, the client device that is the transmission source of the erased plaintext e-mail can retransmit the plaintext e-mail.

  Further, according to the gateway device of the second invention, the control means stores the plain text e-mail decrypted from the encrypted e-mail addressed to the client apparatus transmitted from the mail server apparatus in the volatile storage means. Compared with the prior art, the safety of sending and receiving e-mail can be improved. Furthermore, the control means transmits an e-mail deletion command requesting to delete the encrypted e-mail corresponding to the distributed plain e-mail to the mail server apparatus after distributing the plain e-mail to the client apparatus. To do. Therefore, even if the gateway device is turned off and the plain text email is deleted before the plain text email is delivered to the client device, the erased plain text electronic device is turned on when the gateway device is next turned on. An encrypted electronic mail corresponding to the mail can be received again from the client device.

  Further, according to the gateway device according to the third invention, the control means refers to the received mail management table and searches for a plain text email that has not been transferred to the mail server device based on the transfer processing result code, An error notification mail for notifying that the searched plain text email has not been transferred to the mail server device is created and distributed to the client device that is the transmission source of the searched plain text email. Even if the plain text e-mail stored in the first storage unit is erased, the client device that is the transmission source of the erased plain text e-mail can retransmit the plain text e-mail.

  Still further, according to the gateway device of the fourth invention, the control means requests that the encrypted email corresponding to the delivered plaintext email be deleted after delivering the plaintext email to the client device. An email deletion command is transmitted to the mail server device. Therefore, even if the gateway device is turned off and the plain text email is deleted before the plain text email is delivered to the client device, the erased plain text electronic device is turned on when the gateway device is next turned on. An encrypted electronic mail corresponding to the mail can be received again from the client device.

It is a block diagram which shows the structure of the LAN system provided with the S / MIME gateway apparatus 20 which has a function which transmits / receives an email using S / MIME which is the 1st Embodiment of this invention. It is a block diagram which shows the structure of the client personal computer 30 of FIG. It is a block diagram which shows the structure of the S / MIME gateway apparatus 20 of FIG. It is a block diagram which shows the structure of the mail server apparatus 40 of FIG. It is a figure which shows an example of the item and content of the received mail management data written in each record of the received mail management table 2t of FIG. It is a flowchart which shows the POP3 reception process which concerns on 1st Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG. It is a flowchart which shows the email delivery process which concerns on 1st Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG. It is a flowchart which shows the email transmission process which concerns on 1st Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG. It is a flowchart which shows the error notification mail production | generation process which concerns on 1st Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG. 9 is received by the client personal computer 30 shown in FIG. 2, and the display unit uses the client personal computer 30 program for sending and receiving e-mails. 10 is a front view showing a display example 601 displayed on the screen 104. FIG. 11 receives the error notification mail for notifying the abnormal end of the transmission process generated in step S89 of FIG. 9 by the client personal computer 30 of FIG. 2, and uses the program for sending and receiving e-mails of the client personal computer 30. 7 is a front view showing a display example 701 displayed on the display unit 104. FIG. It is a flowchart which shows the email transfer process which concerns on 2nd Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG. It is a flowchart which shows the error notification mail production | generation process which concerns on 2nd Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG.

Explanation of symbols

1 ... main control part,
2 ... Flash ROM,
2t ... received mail management table,
3… Mail header file memory,
4 ... Mail box for error notification mail,
5 ... Timer circuit,
6 ... ROM,
7 ... SRAM,
8 ... Mail box for receiving POP3,
9 ... Hard disk drive,
10 ... SMTP receiving mailbox,
11 ... Printer,
12 ... LAN interface,
13 ... Bus
20 ... S / MIME gateway device,
30, 30-1 to 30-N ... client personal computer,
40. Mail server device,
60: Router device,
70: Local area network (LAN),
90 ... Internet.

Claims (4)

First storage means for storing plain text e-mail received from the client device;
In a gateway device comprising control means for encrypting the stored plaintext e-mail and transferring it to a mail server device,
Non-volatile second storage means for storing a received mail management table including a relationship between the plain text e-mail and a transfer processing result code indicating whether or not the plain text e-mail has been transferred to the mail server device,
The first storage means is a volatile storage means,
The control means refers to the received mail management table to search for a plain text email that has not been transferred to the mail server device based on the transfer processing result code, and the searched plain text email is the mail server. A gateway device, characterized in that an error notification mail for notifying that a message has not been transferred to the device is created and distributed to the client device that is the transmission source of the searched plain text email. The second storage means further stores a mail header file including a header part of the plain text email,
The received mail management table includes a relationship between the plaintext e-mail, the mail header file, and a transfer processing result code indicating whether or not the plaintext e-mail has been transferred to the mail server device,
2. The gateway device according to claim 1, wherein the control means creates the error notification mail including the contents of a mail header file related to the retrieved plain text electronic mail.   3. The gateway apparatus according to claim 1, wherein the control means stores the error notification mail in the second storage means. First storage means for storing plain text e-mail received from the client device;
In a gateway device comprising control means for encrypting the stored plaintext e-mail and transferring it to a mail server device,
The first storage means is a volatile storage means,
A second storage means for storing a received mail management table including a relationship between the plaintext e-mail and a transfer processing result code indicating whether or not the plaintext e-mail has been transferred to the mail server device;
The control means refers to the received mail management table to search for a plain text email that has not been transferred to the mail server device based on the transfer processing result code, and the searched plain text email is the mail server. A gateway device, characterized in that an error notification mail for notifying that a message has not been transferred to the device is created and distributed to the client device that is the transmission source of the searched plain text email.

Images