JP7463899B2 - Mail control device and program - Google Patents

Description

The present invention relates to an email control technology that encrypts and transmits attachments to emails sent from a terminal.

When important confidential information is included in an email, the erroneous sending of the email becomes a major problem. One method for dealing with such erroneous sending is to include a technique in which, when important confidential information is sent by email, the confidential information is written in an attachment, encrypted with a password, and attached to the outgoing email, and the password is notified to the recipient in a password notification email separate from the outgoing email. This makes it possible to avoid the risk of confidential information leaking, since the attachment cannot be decrypted unless the password notification email is sent to the incorrect recipient (see, for example, Patent Document 1).

In Patent Document 1, an email relay device is configured to encrypt an attachment attached to an email sent from a source terminal, send the encrypted file to a destination terminal, and, based on a notification instruction from the source terminal of the email, generate a password notification email containing an encryption password for decrypting the encrypted file, and send the password notification email to the destination terminal of the email.

In Patent Document 1, an encrypted file obtained by encrypting an attachment from a sending terminal is sent to a destination terminal, and the destination terminal is notified of the encryption password by a separate email, so that only a legitimate terminal can decrypt the encrypted file and obtain the original attachment.

JP 2008-187280 A

If the destination terminal is notified of the encrypted password by a separate email, it is possible to prevent the password notification email from being sent to the incorrect destination if there is an error in the destination of the email. However, the sending terminal must send a separate email to the incorrect destination requesting that the sent email be discarded, which creates a problem of a heavy workload on the sending terminal.

The present invention is intended to solve these problems, and aims to provide an email control device that can reduce the workload on the sending terminal when an error occurs in the destination of an outgoing email.

In order to achieve this object, the mail control device according to the present invention encrypts the attachment and transmits it to a destination terminal when a file is attached to an outgoing mail from a sending terminal, and includes an encryption processing unit that encrypts the attachment, a mail processing unit that transmits the outgoing mail with the encrypted attachment to the destination terminal, a storage unit that stores the outgoing mail with the encrypted attachment, and a password notification processing unit that notifies the sending terminal of a list of destinations of a password notification mail that notifies an encryption password for decrypting the encrypted attachment, and the mail processing unit compares the destination address of the password notification mail created using the destination list of the password notification mail from the sending terminal with the destination address of the outgoing mail stored in the storage unit, creates a discard request mail that requests the discard of the outgoing mail to be sent to a specific destination address that is a destination of the outgoing mail and is not a destination of the password notification mail, and includes one specific destination address or multiple specific destination addresses, and transmits the discard request mail to the destination terminal of the specific destination address.

The email processing unit may also send the discard request email to the source terminal, and after the source terminal confirms the sending of the discard request email, send it to a destination terminal with the specific destination address.

The email processing unit may also notify the sending terminal of the result of sending the discard request email.

The email processing unit may also send the discard request email to the destination terminal of the specific destination address and to the source terminal.

The mail control program according to the present invention is a mail control program executed in a mail control device that encrypts an attachment and sends it to a destination terminal when a file is attached to an outgoing mail from a sending terminal, and causes the mail control device to execute the following steps: an encryption step of encrypting the attachment; a step of sending the outgoing mail with the encrypted attachment to the destination terminal; a storage step of saving the outgoing mail with the encrypted attachment; a notification step of notifying the sending terminal of a list of destinations of a password notification mail that notifies an encryption password for decrypting the encrypted attachment; a comparison step of comparing a destination address of the password notification mail created using the destination list of the password notification mail from the sending terminal with a destination address of the outgoing mail stored in the storage unit; and a transmission step of creating a discard request mail that is sent to a specific destination address that is a destination of the outgoing mail but is not a destination of the password notification mail, the discard request mail containing one specific destination address or multiple specific destination addresses, and sending the discard request mail to a destination terminal of the specific destination address.

According to the present invention, after sending an outgoing email with an encrypted file attached, the sending terminal is notified of a list of destinations for a password notification email notifying the encrypted password, and the destinations of the password notification email created using the list of destinations for the password notification email from the sending terminal are compared with the destinations of the outgoing email. For destinations that do not exist in the password notification email, a discard request email is sent. Therefore, if there is an error in the destination of the outgoing email, the sending terminal does not need to create and send a discard request email, which reduces the workload on the sending terminal.

FIG. 2 is a block diagram showing the configuration of a mail control device. FIG. 2 is an explanatory diagram showing an example of the structure of an outgoing email. FIG. 11 is an explanatory diagram showing an example of the structure of an outgoing email with an encrypted attachment; FIG. 13 is an explanatory diagram showing an example of the structure of a notification email (for sender); FIG. 13 is an explanatory diagram showing an example of the structure of a notification email (for sender) after correction. FIG. 13 is an explanatory diagram showing an example of the structure of a notification email (for a destination). FIG. 11 is an explanatory diagram illustrating an example of the configuration of a discard request email. FIG. 11 is a sequence diagram showing a sending mail control operation.

Next, an embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiment described below.

[Configuration of the mail control device]
An e-mail control device 10 according to the present embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the configuration of the e-mail control device.

As shown in FIG. 1, the mail control device 10 is connected between the sender terminal 20 and the communication network NW, and is a device that controls the e-mails sent and received between the mail server 30 of the communication network NW and the sender terminal 20.

The sender terminal 20 is generally an information terminal such as a PC, tablet, or smartphone, and is connected to the mail control device 10 via a wired or wireless communication line L2. It has the function of sending and receiving e-mails using a mail application installed in response to terminal operations.

The communication network NW is made up of a data communication network such as the Internet, and is connected to a mail server 30 that stores and distributes e-mails, and destination terminals #B, #C, and #D (40) that exchange e-mails with the source terminal #A (20).

When the mail control device 10 of this embodiment receives an outgoing mail including an attachment from the sending terminal 20, it automatically generates a password to encrypt the attachment, and sends the outgoing mail with the encrypted file attached to the destination terminal 40. The encryption password for decrypting the encrypted file is notified to the sending terminal 20 in a password notification mail (for the sender), and the password notification mail (for the sender) includes a list of destination addresses for the password notification mail (for the destination) notifying the encrypted password.

When the sending terminal receives a password notification email (for sender) from the email control device 10, it checks the list that lists the destination addresses notified in the password notification email (for sender), and uses that list to instruct the email control device 10 to send the password notification email (for destination).

When the sending terminal 20 checks the list of destination addresses, it rechecks the destination address of the original outgoing email, thereby preventing the password from being notified to a destination terminal to which the email should not have been sent. If the check reveals an error in the destination address of the outgoing email, the incorrect destination can be deleted from the list of destination addresses when issuing an instruction to send a password notification email (for the destination), so that the password notification email will not be sent to the destination address that erroneously sent the outgoing email.

In this embodiment, the mail control device 10, upon receiving an instruction to send a password notification mail (for destination), compares the original outgoing mail with the destination of the password notification mail (for destination) created using a list of destination addresses, and is configured to send a discard request mail requesting the discarding of the outgoing mail to a specific destination address that does not exist in the password notification mail (for destination). With this configuration, if there is an error in the destination address of the outgoing mail, it is not necessary for the sending terminal to create and send a discard request mail, making it possible to reduce the workload on the sending terminal.

[Configuration of the mail control device]
As shown in FIG. 1, the mail control device 10 mainly comprises a network interface unit (hereinafter referred to as network I/F unit) 11, a terminal interface unit (hereinafter referred to as terminal I/F unit) 12, a memory unit 13, and a control unit 14.

The network I/F unit 11 is a processing unit that transmits and receives various data, such as e-mail-related protocol messages and mail data, between the communication network NW via a wired or wireless communication line L1.

The terminal I/F unit 12 is a processing unit that transmits and receives various data, such as protocol messages and mail data related to e-mail, between the source terminal 20 and the terminal 20 via a wired or wireless communication line L2.

The memory unit 13 is a processing unit that consists of a storage device such as a hard disk or semiconductor memory, and stores various processing data and programs 13P used for mail control processing in the mail control device 10.

Program 13P is a mail control program that realizes various processing units for executing mail control processing by working in cooperation with the CPU of the control unit 14, and is read from an external device or recording medium (neither shown) connected to the mail control device 10 and is stored in advance in the memory unit 13.

[Control unit]
The control unit 14 includes a CPU (central processing unit) and its peripheral units, and realizes various processing units for executing the mail control process by reading out the mail control program from the storage unit 13 and executing it.

The main processing units realized by the control unit 14 are an email processing unit 14A, a password notification processing unit 14B, and an encryption processing unit 14C. These processing units are configured to perform the functions described below, but the relationship between these processing units and functions is not limited to the contents described below, and specific functions may be realized by other processing units.

[Mail processing section]
The mail processing unit 14A has the function of exchanging sent and received mail with the mail server 30 via the communication network NW, the communication line L1, and the network I/F unit 11, the function of exchanging sent and received mail with the sending terminal 20 via the communication line L2 and the terminal I/F unit 12, the function of relaying and forwarding sent mail from the sending terminal 20 to the mail server 30, and the function of relaying and forwarding received mail from the mail server 30 to the sending terminal 20.

In addition, when an attachment is attached to an outgoing email from the sending terminal 20, the email processing unit 14A has the function of temporarily storing the outgoing email, with the attachment encrypted by the encryption processing unit 14C, in the memory unit 13 as a saved email 13A, the function of sending the outgoing email to the email server 30, the function of sending a password notification email (for the sender) sent from the password notification processing unit 14B to the email server 30, and the function of sending a password notification email (for the sender) received from the email server 30 to the sending terminal 20 of the outgoing email.

The mail processing unit 14A also has a function of relaying the password notification mail (for destination) sent from the sending terminal 20 to the mail server 30, a function of acquiring the sent mail from the stored mail 13A in the memory unit 13, and a function of comparing the destination address of the password notification mail (for destination) with the destination address of the sent mail, creating a discard request mail with a specific destination address that does not exist in the password notification mail as the destination, and sending the mail to the mail server 30.

[Password notification processing section]
The password notification processing unit 14B has a function of notifying the sender terminal 20 of the encryption password used in the encryption processing of the attachment in the encryption processing unit 14C by sending a password notification email (for sender) via the email processing unit 14A.

[Encryption Processing Unit]
The encryption processing unit 14C has a function of generating an encryption password to be used for encrypting the attachment when the email processing unit 14A receives an outgoing email with an attachment from the sending terminal 20, a function of encrypting the attachment included in the outgoing email based on the generated encryption password, and a function of sending the encrypted file resulting from encrypting the attachment to the email processing unit 14A.

[Outgoing Mail Configuration]
Fig. 2 is an explanatory diagram showing an example of the structure of an outgoing email. As shown in Fig. 2, an outgoing email is composed of various items such as a sender address (From), a destination address (To, Cc, Bcc), a subject, and an email body, and data indicating the contents. In this example, "aaa@aaa.jp" is specified as the sender address, and three addresses "bbb@bbb.jp", "ccc@ccc.jp", and "ddd@ddd.jp" are specified as the destination addresses.

In addition, important confidential information and other content that is inappropriate to include in the body of the email is stored in a separate electronic file on the sender terminal 20 and attached as an attachment to the outgoing email. In the example of FIG. 2, an attachment with the file name "xxxxxx.doc" is attached to the outgoing email. Specific examples of attachments include document files and drawing files created on a PC, or photo files taken with a camera. This attachment is encrypted with a password automatically generated by the control unit 14, and the outgoing email with the encrypted attachment is sent to the mail server 30.

[Outgoing mail (encryption) configuration]
Fig. 3 is an explanatory diagram showing an example of the structure of an outgoing mail with an encrypted attachment. As shown in Fig. 3, an outgoing mail with an encrypted attachment is composed of various items such as a sender address (From), a destination address (To, Cc, Bcc), a subject, and a mail body, and data showing the contents. The stored mail 13A in the storage unit 13 is an outgoing mail with an encrypted attachment.

In this example, the attachment is replaced with an encrypted file (compressed file) encrypted by encryption processing unit 14C, and the file name is changed to the encrypted file name "xxxxxx.zip". Also, as in FIG. 2, "aaa@aaa.jp" is specified as the source address, and three addresses "bbb@bbb.jp", "ccc@ccc.jp", and "ddd@ddd.jp" are specified as the destination addresses.

[Password notification email (sender) configuration]
Fig. 4 is an explanatory diagram showing an example of the configuration of a password notification email (for sender). As shown in Fig. 4, a password notification email (for sender) is composed of various items such as a sender address (From), a destination address (To, Cc), a subject, and an email body, and data showing the contents. In this example, "aaa@aaa.jp", which is the sender address of the outgoing email, is specified as the sender address, and "aaa@aaa.jp", which is the same as the sender address, is written as the destination address.

The subject line also reads "Password notification email (for sender)," making it clear that the email is a password notification email for the sender to notify the sender's device of the password.

The email text also contains an explanation of the password notification email for the sender, the password to be sent in this password notification email (for the sender), an explanation of the details of the sent email to identify the sent email, and a list of destinations for the password notification email (for the recipient). In the example of Figure 4, the contents of the sent email sent from the sender address "aaa@aaa.jp" to the destination addresses "bbb@bbb.jp", "ccc@ccc.jp", and "ddd@ddd.jp" and the list of destinations for the password notification email (for the recipient), "bbb@bbb.jp", "ccc@ccc.jp", and "ddd@ddd.jp", are listed.

The sender terminal 20 can recheck the destination address specified in the sent email by checking the contents of the sent email written in the body of the email in FIG. 4. If the destination address of the sent email is incorrect, the sender terminal 20 can check the destination list of the password notification email (for destinations) and delete the incorrect destination address to correct the destination list of the password notification email (for destinations).

Figure 5 is an explanatory diagram showing an example of the configuration of a password notification email (for sender) with a corrected destination list. In the example of Figure 5, the destination address "To: bbb@bbb.jp" can be recognized as an incorrect destination address, so the destination list of the password notification email (for recipient) can be easily corrected by checking the destination list of the password notification email (for recipient) and deleting the incorrect destination address "To: bbb@bbb.jp" from the destination list of the password notification email (for recipient). This makes it possible to configure the password notification email (for recipient) not to be sent to the incorrect destination address "To: bbb@bbb.jp".

In this embodiment, a separate password is generated for each outgoing email and is used commonly for multiple destination addresses included in the outgoing email, but this is not limited to the above. For example, to increase the security of attachments, a separate password may be generated for each destination address included in the outgoing email.

[Password notification email (for recipient)]
Fig. 6 is an explanatory diagram showing an example of the configuration of a password notification email (for recipient). As shown in Fig. 6, the password notification email (for recipient) is composed of various items such as a sender address (From), a recipient address (To, Cc, Bcc), a subject, and an email body, and data showing the contents. In this example, "aaa@aaa.jp", which is the sender of the password notification email (for recipient), is specified as the sender address.

The subject line also reads "Password notification email (for recipient)," making it clear that the email is a password notification email for the recipient to notify the password of the destination device of the outgoing email.

The email body also contains an explanation about the password notification email for the recipient, the password to be sent in this password notification email (for the recipient), and details about the sending email to identify the sent email.

Here, the mail control device 10 can create a password notification mail (for destination) using the destination list of the password notification mail (for sender) sent from the sender terminal 20 so that the password notification mail (for destination) is sent only to the correct destination. As a result, the mail control device 10 sends the password notification mail (for destination) only to the correct destination address corrected in the destination list of the password notification mail from the sender terminal 20.

In the example of Figure 6, the destination addresses "Cc: ccc@ccc.jp" and "Bcc: ddd@ddd.jp" are correct destination addresses, so they are listed in the same way as in the password notification email (for sender). On the other hand, the destination address "To: bbb@bbb.jp" is an incorrect destination address and has been deleted from the destination list, so it has been deleted from the password notification email (for recipient).

[Configuration of the deletion request email]
The mail processing unit 14A retrieves the sent mail (FIG. 3) of the stored mail 13A from the storage unit 13, and compares the destination address of the password notification mail (for destination) (FIG. 6) with the destination address of the sent mail. If the comparison result indicates that the destination address of the sent mail includes a specific destination address that does not exist in the password notification mail (for destination), a discard request mail is created with the destination address as the destination, and is sent to the mail server 30.

Figure 7 shows an example of the structure of a destruction request email. As shown in Figure 7, a destruction request email is composed of various items such as the sender address (From), the destination address (To), the subject, and the email body, as well as data indicating the contents of those items.

The subject of the email reads "Deletion Request Email," making it clear that the email is an email to request the destination device to delete the email. The body of the email contains an explanation that the email was sent by mistake and provides details about the email.

In this example, a comparison of the destination address of the password notification email (for destination) (Figure 5) with the destination address of the outgoing email (Figure 3) reveals that the destination address of the outgoing email is "bbb@bbb.jp", which does not exist in the password notification email (for destination), so the destination address of the discard request email is "To:bbb@bbb.jp", the destination address to which the outgoing email was sent in error. The discard request email is sent from the email control device 10 to the email server 30, and then to the destination terminal 40 corresponding to that destination address.

In FIG. 7, an example is described in which the destination address of the outgoing email contains one specific destination address that does not exist in the password notification email (for destination). Even if there are multiple specific destination addresses, multiple discard request emails containing one specific destination address may be created, or a discard request email containing multiple specific destination addresses may be created.

[Operation of the mail control device according to this embodiment]
The operation of the mail control device 10 according to the present embodiment will be described with reference to Fig. 8. Fig. 8 is a sequence diagram showing the outgoing mail control operation. The mail control program stored in program 13P causes the mail control device 10 to execute each step in the following sequence.

When sender terminal #A creates an email with an attachment (step S100) and performs a send operation (step S101), the email is sent from sender terminal #A to the email control device 10 (step S102).

The mail processing unit 14A of the mail control device 10 receives an outgoing mail with an attachment in response to a mail sending request from sender terminal #A. In the example of FIG. 2, the sender address of the outgoing mail is "aaa@aaa.jp", the destination addresses are "bbb@bbb.jp" and "ccc@ccc.jp", and the file attached is "xxxxxx.doc".

The encryption processing unit 14C generates an encryption password to be used to encrypt the attachment for each outgoing email received by the email processing unit 14A (step S103). In the example of FIG. 4, the encryption password "hagr21vas" is generated.

The encryption processing unit 14C encrypts the attached file using the generated encryption password (encryption step) (step S104), and the mail processing unit 14A sends the outgoing mail with the encrypted file attached to the mail server (step S105). The mail processing unit 14A stores the outgoing mail as saved mail 13A in the memory unit 13 (save step) (step S106). In the example of FIG. 3, the outgoing mail with the encrypted file "xxxxxx.zip", which is the encrypted file "xxxxxx.doc", attached is sent and saved.

The password notification processing unit 14B creates a password notification email (for sender) containing a list of recipients of the password notification email (for recipient) as shown in FIG. 4 as an email to notify the sender terminal #A of the encryption password used to encrypt the attachment (step S107), and the email processing unit 14A sends this password notification email (for sender) to the email server via the network I/F unit 11, communication line L1, and communication network NW (step S108).

Then, the mail processing unit 14A receives a password notification mail (for the sender) from the mail server 30 via the communication network NW, the communication line L1, and the network I/F unit 11, and delivers it to the sender terminal #A via the terminal I/F unit 12 and the communication line L2 (notification step) (step S109).

The sender terminal #A checks the password notification email (for sender) received from the email control device 10, checks the destination address specified in the sent email based on the contents of the password notification email body, checks the destination list of the password notification email (for recipient), and modifies the destination address if necessary (step S110).

On the sender terminal #A, the erroneously sent destination address is deleted from the destination list, and the destination list of the password notification mail (destination) with the correct destination address is sent (step S111). As a result, the mail control device 10 receives the corrected destination list of the password notification mail (for destination) from the sender terminal #A (step S112).

In the example of Figure 4, if the destination addresses "Cc: ccc @ ccc.jp" and "Bcc: ddd @ ddd.jp" are correct destinations and the destination address "To: bbb @ bbb.jp" is incorrect, as shown in Figure 5, the destination address "bbb @ bbb.jp" will be deleted from the destination list sent from sender terminal #A, and the destination list for the password notification email (for destination) will be corrected to "Cc: ccc @ ccc.jp" and "Bcc: ddd @ ddd.jp".

When the mail processing unit 14A receives the destination list of the password notification mail (for the destination) from the sending terminal #A, it creates the password notification mail (for the destination) using the confirmed/corrected destination list (step S113) and sends it to the mail server (step S114).

Destination terminal #C receives the password notification email (for the destination) from sender terminal #A via mail server 30, and based on the password stated in the password notification email (for the destination), can decrypt (unzip) the attachment attached to the outgoing mail and open the original attachment. On the other hand, destination terminal #B cannot receive the password notification email (for the destination) from sender terminal #A via mail server 30, and therefore cannot decrypt (unzip) the attachment attached to the outgoing mail.

The email processing unit 14A further retrieves the outgoing email corresponding to the password notification email (for destination) from the stored email 13A in the memory unit 13, and compares the password notification email (for destination) with the destination address of the outgoing email (comparison step) (step S120).

If the comparison shows that the destination address of the outgoing email contains a specific destination address that does not exist in the password notification email (for destination), a discard request email is created with that destination address as the destination (step S121) and is sent to the mail server 30 (sending step) (step S122).

In the example of Figure 7, a comparison of the destination address of the password notification email (for destination) (Figure 6) with the destination address of the outgoing email (Figure 3) reveals that the destination address of the outgoing email is "bbb@bbb.jp", which does not exist in the password notification email (for destination), so the destination address of the discard request email is "To:bbb@bbb.jp", the destination address to which the outgoing email was sent in error. The discard request email is sent from the email control device to the email server 30, and then to the destination terminal #B.

Regarding "bbb@bbb.jp" specified as the destination address in the outgoing email, if the sending terminal realizes that it was sent erroneously and does not send a password notification email from sending terminal #A, the email control device 10 will not send a password notification email to the destination address "bbb@bbb.jp". Instead, the email control device 10 will send a discard request email to the erroneous destination "bbb@bbb.jp".

In FIG. 8, the mail control device creates a discard request email and sends it to the erroneously sent destination address. However, the discard request email may be sent to the sending terminal before sending, and may be sent after the sending terminal confirms the contents and sending of the discard request email.

The email control device may also notify the sending terminal of the result of sending the discard request email, or may send the discard request email to the sending terminal and the destination terminal of a specific destination address.

[Effects of this embodiment]
In this way, according to this embodiment, after sending an outgoing email with an encrypted file attached, the sending terminal is notified of a list of destinations for password notification emails that notify the encryption password for decrypting the encrypted attachment, and the destinations of the password notification email created using the list of destinations for the password notification email from the sending terminal are compared with the destinations of the outgoing email, and a discard request email is sent to any destinations of the outgoing email that do not exist in the password notification email.Therefore, if there is an error in the destination of the outgoing email, it is not necessary for the sending terminal to create and send a discard request email, making it possible to reduce the workload on the sending terminal.

[Extended embodiments]
Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-mentioned embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. In addition, the respective embodiments can be implemented in any combination within a range that does not contradict each other.

10...mail control device, 11...network interface unit (network I/F unit), 12...terminal interface unit (terminal I/F unit), 13...storage unit, 13A...stored mail, 13P...program, 14...control unit, 14A...mail processing unit, 14B...password notification processing unit, 14C...encryption processing unit, 20...sender terminal, 30...mail server, 40...destination terminal, L1, L2...communication line, NW...communication network.

Claims (5)

In a mail control device, when a file is attached to an email sent from a sending terminal, the attached file is encrypted and sent to a destination terminal,
an encryption processing unit that encrypts the attached file;
a mail processing unit that transmits the outgoing mail with the encrypted attachment to the destination terminal;
a storage unit for storing the outgoing email with the encrypted attachment;
a password notification processing unit that notifies the transmission source terminal of a list of destinations of a password notification mail that notifies the transmission source terminal of an encryption password for decrypting the encrypted attachment;
The mail processing unit includes:
comparing a destination address of the password notification mail created using a destination list of the password notification mail from the sender terminal with a destination address of the outgoing mail stored in the storage unit;
An email control device creates an email requesting the destruction of the outgoing email, the email being sent to a specific destination address that is the destination of the outgoing email and is not the destination of the password notification email, the email containing one specific destination address or multiple specific destination addresses, and sends the email to a destination terminal of the specific destination addresses. The mail processing unit includes:
2. The mail control device according to claim 1, further comprising: a mail control unit that transmits the discard request mail to the transmission source terminal; and, after the transmission of the discard request mail is confirmed by the transmission source terminal, transmits the discard request mail to a destination terminal of the specific destination address. 3. The mail control device according to claim 1, wherein the mail processing unit notifies the sending terminal of a result of sending the discard request mail. 4. The mail control device according to claim 1, wherein the mail processing unit transmits the discard request mail to a destination terminal of the specific destination address and to the source terminal. A mail control program executed in a mail control device that encrypts an attached file and transmits the file to a destination terminal when a file is attached to an outgoing mail from a sending terminal,
an encryption step of encrypting the attachment;
sending the outgoing mail with the encrypted attachment to the destination terminal;
a storage step of storing the transmitted email with the encrypted attachment;
a notification step of notifying the transmission source terminal of a list of destinations of a password notification mail notifying the encryption password for decrypting the encrypted attached file;
a comparison step of comparing a destination address of the password notification mail created using a destination list of the password notification mail from the sender terminal with a destination address of the outgoing mail stored in the storage step;
a sending step of sending an email requesting the discarding of the sent email to a specific destination address that is a destination of the sent email and is not a destination of the password notification email, the sending step being to create a discard request email containing one of the specific destination addresses or multiple specific destination addresses, and sending the email to a destination terminal of the specific destination addresses.

Images