JP2004139170A - E-mail system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical security system for distributing, for example, image data by an e-mail. <P>SOLUTION: The system comprises a mail server 4 having a means of creating an identification code unique for each e-mail and then creating header information encoded based on a specific algorithm and a means of distributing an e-mail including the header information and link information to a content distribution server to a user's terminal; and a content distribution server 7 having a means of distributing contents and a means of transmitting a processing program for reproducing the contents. The system further comprises a user terminal device 2 having a means of decoding the header information of an e-mail, a means of managing whether or not link to the content distribution server is performed based on the header information, a means of receiving the contents from the content distribution server, a means of receiving a processing program for reproducing the contents and a content reproducing means of reproducing the contents. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an e-mail system for distributing various contents such as multimedia information by e-mail, and more particularly, to an e-mail system having a function of restricting distribution of contents to non-authorized recipients.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, image transmission has been performed using electronic mail with a feeling similar to that of faxing. For example, FIGS. 6 and 7 show examples of image transfer using an electronic mail system described in Patent Document 1. This communication system uses a network-connected image input function called an Internet copier and the like, and a mail. It has a server function such as a server and an e-mail transmission function. FIG. 6 shows processing on the transmission side (server side). The transmission operator sets, for example, four transmission originals in the transmission device (S200). ). The four originals may be of a DM (direct mail) type or an office type.
Transmission setting is performed from the operation unit according to the display on the display unit (S201).
[0003]
Here, when the transmission operator specifies the mail address of the transmission destination and presses the start button (S202), the image input unit starts reading the image (S203). The read image data is stored in a memory in a file in a predetermined format (S204). Next, based on the mail address of the transmission destination, it is determined whether the transmission destination is a receiving terminal connected to the Internet or a terminal connected to a dedicated line (S205). In the case of the Internet connection, a URL (Uniform Resource Locator) to be a request for receiving the Internet is generated (S206), and in the case of the intranet, a local URL is generated (S208).
[0004]
Next, an e-mail message to be transmitted to the set destination e-mail address is created (S207). This e-mail message contains a message or the like that prompts the recipient to access the WWW browser based on the URL described in the main text, and furthermore, an e-mail message that describes the reception URL generated in S206 as the URL. Generate.
This e-mail message usually includes a header part and a body, and the header describes a sender, a recipient, date and time, data information, and the like. Please click the URL for receiving. " If the recipient clicks the URL, the image can be received.
The generated e-mail message is transferred to a predetermined mail server, and the process ends (S209).
[0005]
FIG. 7 is a flowchart of the receiving process on the WWW browser side. First, the receiving terminal displays the text of the received e-mail message and checks the display contents (S300). The text of the received e-mail contains the URL for reception, and in addition, text that prompts the browser to access this URL, information on the sender, and the like.
Does the operator see the displayed contents and receive the transmitted data? Is determined (S301). If not, the process ends. On the other hand, when receiving, the browser is started (S302), and receiving is instructed by the receiving URL (S303). Generally, the browser automatically determines whether the URL indicates "http" (a normal HTTP protocol that does not perform security processing) or "https" (a secure protocol that performs encryption processing), and requests a data request or the like. Perform playback processing.
After waiting for a response to the transmission and completing the data reception (S304), the browser displays the received image (S305), confirms the received data (S306), and ends the processing.
[0006]
In the above-described conventional technology, in order to maintain high security by performing data encryption processing, for example, when transmitting image data or the like, a client is transmitted using an HTTPS (Hyper Text Transfer Protocol over SSL). A method of establishing an SSL (Secure Sockets Layer) connection using encryption processing between a server and a server, and then performing a data transfer by HTTP, thereby preventing data tapping and falsification and realizing secure data exchange. Is possible. In the case of e-mail, POP (Post Office Protocol) using POP / SMTP over SSL or SSL corresponding to SMTP (Simple Mail Transfer Protocol) can be used.
[0007]
Further, as security of Internet e-mail, a method of encryption processing using S / MIME (Secure Multi-Purpose Internet Mail Extensions), PGP (Pretty Good Privacy), and the like, and an electronic signature method are known.
S / MIME uses an RSA encryption method developed by RSA Security as a public key encryption method. A sender performs an encryption process using a public key, and a receiver uses a secret key to read a message. At this time, an electronic certificate issued by the certification organization is required. PGP is an encryption method combining a common key method and a public key encryption method, and has functions such as encryption of an e-mail message and an electronic signature.
[0008]
[Patent Document 1]
JP-A-2002-135291 (pages 19 to 20, FIGS. 3 and 4)
[0009]
[Problems to be solved by the invention]
However, in SSL, the transmitting side encrypts data to be transmitted using a digital certificate to be authenticated by the receiving side, and decrypts the encrypted data at the receiving terminal through an SSL connection. It is intended to guarantee the security of data on the communication line to be delivered, but not for the electronic mail itself. Also, in order to decrypt an e-mail message, agreements and procedures between a sender and a receiver are required in advance.
Furthermore, a huge amount of data such as image content and 3D image content using encryption / decryption processing such as SSL, S / MIME, and PGP may cause a waiting time for a user due to an increase in load in the encryption / decryption processing. There is a problem that it imposes the burden of increasing
In addition, there is no means for confirming from the receiver side whether the content distributor is a legitimate content right holder, and there is also a problem that the legitimate distribution route cannot be maintained.
[0010]
Therefore, the present invention enables only authorized recipients to receive content distribution by e-mail without special procedures in advance, further embeds authorized domain information in the content, and confirms the authorized distributor. It is therefore an object of the present invention to provide an e-mail system capable of preserving a normal distribution route, constructing practical security between a distribution side and a reception side and distributing contents.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a computer system that distributes contents such as still images, moving images, 3D images, animations, videos, and music by e-mail via a communication network, A mail server for delivering an e-mail to a receiving user, a content delivery server for delivering the content, and a receiving user terminal for the receiving user to receive the email and the content And a device,
The mail server generates a unique identification code for each e-mail to be transmitted, and header information for generating header information obtained by encoding information including at least the identification code and the destination of the e-mail based on a specific algorithm. Generating means; and mail distributing means for distributing a hypertext e-mail including the header information and the link information to the content distribution server to a receiving user terminal device, wherein the content distribution server comprises: Content distribution means for distributing the content to the receiving user terminal device by being called from the hypertext of the mail, and a content processing program for transmitting a processing program for receiving and reproducing the content on the receiving user terminal device Transmitting means,
The receiving-side user terminal device receives an e-mail transmitted from the mail server, and decodes header information encoded based on a specific algorithm included in the e-mail to obtain necessary information. Header information obtaining means, link management means for managing whether or not to link to a content distribution server based on the header information obtained by the header information obtaining means and the hypertext link information of the electronic mail; Content receiving means for linking by link management means and receiving content from the content distribution server, content processing program receiving means for receiving a processing program for receiving and reproducing content from the content distribution server, and the content processing program Received and re- It is characterized by having a content reproducing means for, the.
[0012]
According to a second aspect of the present invention, there is provided a computer system for distributing contents such as still images, moving images, 3D images, animations, videos, and music by e-mail via a communication network. A transmitting-side user terminal device for transmitting the e-mail and the content, a mail server for receiving an e-mail from the transmitting-side user and delivering the e-mail to a receiving-side user; A content distribution server for distributing, and a receiving user terminal device for the receiving user to receive the e-mail and the content,
The transmitting-side user terminal device generates a unique identification code for each e-mail to be transmitted, and generates header information obtained by encoding information including at least the identification code and the destination of the e-mail based on a specific algorithm. Header information generating means for generating, and mail transmitting means for transmitting a hypertext e-mail including the header information and the link information to the content distribution server to a mail server, the mail server comprising: Mail distribution means for distributing a hypertext e-mail including the header information from the user terminal device and link information to the content distribution server to a receiving user terminal device,
The content distribution server is a content distribution unit that distributes the content to the receiving user terminal device by being called from the hypertext of the email, and a content distribution server that receives and reproduces the content with the receiving user terminal device. Content processing program transmitting means for transmitting the processing program,
The receiving-side user terminal device receives an e-mail transmitted from the mail server, and decodes header information encoded based on a specific algorithm included in the e-mail to obtain necessary information. Header information obtaining means, link management means for managing whether or not to link to a content distribution server based on the header information obtained by the header information obtaining means and the hypertext link information of the electronic mail; Content receiving means for linking by link management means and receiving content from the content distribution server, content processing program receiving means for receiving a processing program for receiving and reproducing content from the content distribution server, and the content processing program Received and re- It is characterized by having a content reproducing means for, the.
[0013]
The content distribution server according to claim 3, further comprising domain information embedding means for embedding domain information of the distribution server in the content, wherein the receiving-side user terminal device embeds the content in the content. It is characterized by having domain information matching means for comparing the inserted domain information with the domain of the content distribution server of the distribution source to identify unauthorized distribution.
The decoding algorithm of the header information according to claim 4 is supplied to the recipient-side user terminal device as hypertext information of an electronic mail or as an attached file of the electronic mail. And
Further, the link management program to the content distribution server in the link management means according to claim 5 is included in a decoding algorithm of header information of an email, or supplied as hypertext information of the email, or It is either supplied as an e-mail attachment.
Further, the contents distributed by the e-mail according to claim 6 are characterized in that the contents are three-dimensional animations by a computer graphic corresponding to an HTML browser which can be operated interactively by a receiving user. A content processing program for receiving content from the content distribution server and reproducing the content on a receiving user terminal device according to claim 7, is a Java (R) program called by hypertext link information of an electronic mail. It is an applet.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an electronic mail system according to a first embodiment of the present invention.
FIG. 3 is a flowchart of the processing on the distribution side shown in FIG.
FIG. 4 is a flowchart of the process on the receiving side shown in FIG.
In FIG. 1, reference numeral 1 denotes a system center formed by a computer system including a server for distributing contents via a network 3. Reference numeral 2 denotes a receiving-side user terminal device that receives a content distribution service via a communication network 3 such as the Internet.
[0015]
Reference numeral 4 denotes a mail server on the distribution side, which distributes mail based on the mail address. The mail server 4 stores, for example, a message ID as a unique identification code assigned to each electronic mail, header information such as a mail attribute, a destination, and a title, and a message ID, a destination, a title, and the like from the header information. A header that generates encoding information using various encryption algorithms such as a method that performs a hash function processing by converting a random number table, and a header that incorporates the generated encoding information into the header information. It has an information generation means 5 and a mail distribution means 6 for managing transmission and reception of this e-mail including encrypted header information.
The encryption software program and the encryption algorithm are encrypted using a predetermined algorithm by various encryption methods using the encryption library 17 (which may be downloaded from the Internet).
[0016]
Reference numeral 7 denotes animation 3D image data based on still image data in a JPEG file, moving image data in an MPEG file, and 3DA file (in the present embodiment, a 3D data file for displaying a 3D image in an HTML browser is referred to as a 3DA file). , A content distribution server that distributes various contents such as music data by MPEG audio files in various file formats. The content distribution server 7 includes domain information embedding means 8 for embedding domain information of a legitimate content distribution server in the content. , A content distribution means 9 for distributing image contents called by an e-mail document via the communication network 3, and a decoding container such as an applet for reproducing JPEG, MPEG, and 3DA files, and a viewer. A content processing program transmission means 10 for distributing the tool reproduction information and the like, a content database 18 stores various contents for distribution, in being configured. Reference numeral 19 denotes a database server which manages data access to the cryptographic library 17 and content data. The encryption decode key and the encryption decode (decryption) algorithm are incorporated in the electronic mail or transmitted to the user terminal device 2 on the receiving side by the content processing program transmission means 10. Although the mail server 4 and the content distribution server are configured in the same system center in the present embodiment, they may be configured as separate systems.
[0017]
The mail server 4, the content distribution server 7, the database server 19, and the user terminal device 2 in the system center 1 are configured using a workstation or a commercially available PC (personal computer). (Central Control Unit), a storage device such as a memory and a hard disk, a display device for displaying images and text, an input device such as a keyboard and a mouse, and an input / output device for a communication line and the like. The drawings are omitted.
[0018]
The user terminal devices 2 to n on the receiving side are an unspecified number of user terminal devices. The user terminal devices 2 to n receive the e-mail distributed from the system center 1 and perform encryption decoding (decryption) of the header information. A header information acquiring unit 11 for extracting a title and the like; a link managing unit 12 for managing a URL link of a content distribution source described in an e-mail text based on information from the header information acquiring unit 11 that has decrypted the encrypted data; It has a content processing program receiving means 13 for receiving an applet for reproducing a 3DA file, an encryption decoding key, and the like. The decode key of the header information of the electronic mail is received in the electronic mail document or as an attached file, or from the mail server 4 or the like via the content processing program receiving means 13.
The received content is authenticated by the domain information matching means 14 by the domain information embedding means 8 by the domain information embedding means 8 in the content of the image file or the like, and the domain information of the URL of the distribution source described in the body of the e-mail Is checked to see if it is legitimate delivery. The content received by the content receiving means 15 is reproduced by a content reproducing means 16 such as a player software program for each content.
[0019]
Next, the operation will be described with reference to the flowcharts of FIGS.
First, as shown in FIG. 3, the system center 1 prepares all data necessary for content distribution, and the content distribution server 7 reads image content to be distributed from the content database 18 (S20).
Subsequently, the domain information embedding unit 8 embeds the domain information of the provider recognized by the right holder of the content for verification in a predetermined area of the read content (S21).
[0020]
Next, when distribution of the content is started (S30), the mail address of the receiving side previously acquired by the mail server 4 is set (S31). The header information generation means 5 generates a unique message ID that uniquely identifies the electronic mail (S32), and encrypts the generated message ID, destination, title, and other header information based on a specific algorithm. One piece of encoded information is generated. The generated encoded information is added to the header information as new information (S33).
Encryption is performed using an encryption software program stored in the encryption library 17. The cryptographic library 17 uses an encryption method such as XOR processing or the like, and encryption by scramble processing such as DES (Data Encryption Standard) of the US government standard encryption method, the above-mentioned RSA, other public key methods, and digital watermarking. It has a code and an encryption software program.
[0021]
Next, the mail distribution means 6 creates an HTML (Hyper Text Markup Language) e-mail document having the encrypted header information and the URL link of the content distribution source (S34), and sends it to the destination user terminal 2 at the destination. It is transmitted (S35).
[0022]
Referring to FIG. 4, the receiving side terminal device 2 receives the electronic mail (S40), and decodes the encoded information included in the electronic mail header (S41). In this case, the decoding key and the decoding algorithm are received as an e-mail text or an attached file, or through another channel such as the content processing program receiving means 13.
Decodes the encoded information in the received e-mail header, and compares the decoded information such as the message ID, destination, and title obtained from the decoding result with the original message ID, destination, and title included in the header information. Then, it is checked by the link management means 12 whether they match (S42). The program of the link management means 12 is incorporated in an electronic mail or obtained by the content processing program receiving means 13 or the like.
[0023]
If the decryption information and the original header information do not match, an HTML browser is started by an HTML-compatible e-mail software program, and only the text other than the content is displayed in a state where the content such as image data cannot be received. (S44).
The link to the content distribution source is blocked by the link management means 12 and the content cannot be reproduced, but at this time, the link is not blocked and a message indicating that the mail is not correctly distributed instead of the content reproduction is displayed. You may do it.
[0024]
If the decrypted information matches the original header information, the HTML browser is started (S43), and the content processing program portion for content reproduction, such as an image display program, is sent to the distribution source URL by the content processing program receiving means 13. It is received from the link destination (S45). At this time, the content distribution server 7 distributes the content processing program via the content processing program transmission means 10. From the content processing program, a domain matching unit 14, a content receiving unit 15, and a content reproducing unit 16 are obtained.
The content processing program in this case is, for example, JPEG for a still image, MPEG for a moving image, MPEG Audio for audio content, and a 3DA applet for a 3D image (3DA applet in the present embodiment). An applet for reading a file and displaying a 3D image is referred to as a 3DA applet).
The content processing program receives the content such as image data via the content receiving means 15 (S46). At this time, the content distribution server 7 distributes the requested content via the content distribution means 9.
[0025]
Next, a case where a 3D image is displayed will be described as an example of a case where the distribution content is a 3DA file (other content may be used).
The domain information embedded in the content is compared by the domain information matching means 14 with the domain information of the content distribution server 7 which has been previously approved by the content right company to be received by the recipient's user terminal device 2 in a contract procedure or the like. (S47). If the domains match, a normal 3D image is displayed without displaying the license mark (S48).
If the domain information collation fails in S47, a warning is issued by displaying a license mark (S49). As a result, the user can confirm that the distribution contents are not those of the legitimate right holder, and by clicking on the license mark, connects to the legitimate right holder's HP screen and goes through the legitimate procedures, formal billing procedures, etc. Can be performed (S50).
[0026]
FIG. 5 is an explanatory diagram showing specific contents of the electronic mail document.
An e-mail includes a header section 31 and a mail text 32. The header section 31 includes various types of fields depending on an e-mail software program, a mail server, or a mail transfer path.
The main items are Received 101 indicating the route information of the server, Date 102 of the transmission date and time, From 103 indicating the mail address of the sender, To 104 indicating the mail address of the destination, Subject 105 indicating the title (title and subject) of the mail, and distinguishing the mail. Fields such as a Message-Id 106, a MIME-Version 108, and a Content-Type 109 indicating the format of the body of a mail message. MIME (Multipurpose Internet Mail Extensions) is a rule for sending multimedia information by e-mail, and text / html of Content-Type 109 indicates that the message body is written in HTML format.
[0027]
In the present embodiment, the unique Message-Id 105, the destination To 104, and the Subject 105 from the header information are encrypted by an encryption algorithm, and the generated encoded information is stored in the header field on the transmission side as an X-Message-Id 107. It is added and decrypted at the receiving end, and compared with the original information.
E-mail software programs that support the HTML format include those that start and display an HTML browser in an e-mail display window, those that start another Web browser, and those that right-click the text display window with a mouse. Depending on the HTML file, any method may be used as long as the HTML file is interpreted and browsed.
[0028]
The header information is taken out by the ActiveX control. ActiveX realizes a dynamic Web page, and a Java (R) applet has almost the same function. The Java (R) applet extracts header information of an existing e-mail software program which is widely used. Because it is not possible, the ActiveX control is used.
<Object class = “CLSID: XXXXXXXXX-...” To </ object>, corresponding to 301 to 302, extract header information by describing a script (not shown), and “codebase” indicates saving of the ActiveX control. Although the location is indicated, it is not necessary to describe the location if it is included in the OS (Operating System).
[0029]
The content from the distribution server is downloaded and played by executing a Java (R) applet called by an applet tag described in HTML.
<Apple code = “Applet3da.class”...> To </ applet> 401 to 404 are examples of displaying a 3D image by processing a 3DA file using a 3DA applet in a corresponding portion. “Codebase” indicates the storage location of the applet, and an applet class file for a 3DA file is downloaded from the file indicated by “archive” to display a 3D image. License information is embedded in the 3DA file. 402 example. 3da is a 3DA file, and the default. Reference numeral tbf denotes a toolbar file for performing an interactive operation with the user, for operating a 3D scene of a 3D image.
[0030]
Note that the decryption algorithm for decryption and the link management program for content with the distribution server can be obtained by calling the ActiveX control or calling another Java (R) applet (not shown).
Regarding link management, in practice, the content is directly called by embedding the link management information in the code class file or dynamically changing the storage location of the codebase, and reading the HTML source. Keep it away.
[0031]
Next, an e-mail system according to a second embodiment of the present invention will be described with reference to the configuration diagram of FIG.
In FIG. 2, reference numeral 20 denotes a transmitting-side user terminal device for transmitting a mail. Reference numeral 21 denotes a header information generation unit of the transmission-side user terminal device 20, and reference numeral 22 denotes a mail transmission unit. The transmission-side user terminal 20 does not particularly have an encryption library, and the encryption algorithm applied to the present system is incorporated in the header information generation means 20 as a software program.
The same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.
[0032]
In the case of FIG. 2, the header information generating means 21 of the user terminal device 20 on the transmitting side creates an e-mail for the user terminal device 2 on the receiving side in a mail document format as shown in FIG. The e-mail is transmitted from the mail transmitting means 22 to the user terminal device 2 on the receiving side via the mail server 4. The user terminal device 2 on the receiving side that has received the e-mail reads the header information of the e-mail by the header information obtaining means 11 and performs a content distribution request when the first embodiment shown in FIG. The content is received, the domain information is collated, and the content is displayed by a similar procedure and procedure.
[0033]
【The invention's effect】
As described above, according to the present invention, an HTML mail is transmitted by adding a unique ID, a destination, and encoded information generated by encrypting a title from the header information of an email to the original header. Then, on the receiving side, the encoded information is decoded and compared with the original header information to determine that the received mail is legitimate, and only when the header information matches, the content is transmitted from the distribution server at the link destination of the HTML mail. In addition, it is configured to receive content, and since the domain embedded in the distributed content is compared with the domain of the distribution source to identify unauthorized distribution, the non-encryption of the content itself, which increases processing time, is performed. An e-mail system that allows only legitimate recipients to receive and avoid content reproduction even when transferred, avoiding practical processes It is possible to improve the utility, furthermore, confirms the legitimate rights of the content, there is an effect that it is possible to prevent the distribution of illegal content.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an electronic mail system according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of an electronic mail system according to a second embodiment of the present invention.
FIG. 3 is a flowchart of processing on the distribution side shown in FIG. 1;
FIG. 4 is a flowchart of processing on the receiving side shown in FIG. 1;
FIG. 5 is an explanatory diagram showing the contents of an e-mail document.
FIG. 6 is a flowchart of a distribution process of a conventional distribution system.
FIG. 7 is a flowchart of a reception process of a conventional distribution system.
[Explanation of symbols]
1 system center
2,20 user terminal device
3 communication network
4 mail server
5, 21 header information generating means
6 Mail delivery means
7 Content distribution server
8 Domain information embedding means
9 Content distribution means
10 Content processing program transmission means
11 Header information acquisition means
12 Link management means
13 Content processing program receiving means
14 Domain information matching means
15 Content receiving means
16 Content playback means
17 Cryptographic Library
18 Content Database
19 Database server
22 Mail transmission means

Claims (7)

A computer system for delivering content such as still images, moving images, 3D images, animations, videos, and music by e-mail via a communication network,
A mail server for delivering e-mail to the receiving user,
A content distribution server for distributing the content,
A receiving user terminal device for the receiving user to receive the e-mail and the content,
The mail server generates a unique identification code for each e-mail to be transmitted, and header information for generating header information obtained by encoding information including at least the identification code and the destination of the e-mail based on a specific algorithm. Generating means;
Mail distribution means for distributing a hypertext e-mail including the header information and the link information to the content distribution server to a receiving-side user terminal device,
The content delivery server, content delivery means for delivering the content to the receiving user terminal device by being called from the hypertext of the email,
Content processing program transmitting means for transmitting a processing program for receiving and reproducing the content at the receiving user terminal device,
The receiving-side user terminal device receives an e-mail transmitted from the mail server, and decodes header information encoded based on a specific algorithm included in the e-mail to obtain necessary information. Header information acquisition means,
Link management means for managing whether or not to link to a content distribution server based on the header information obtained by the header information acquisition means and the hypertext link information of the electronic mail;
Content receiving means for performing a link by the link management means and receiving content from the content distribution server,
Content processing program receiving means for receiving a processing program for receiving and reproducing content from the content distribution server,
An e-mail system comprising: a content reproducing unit that receives and reproduces the content according to the content processing program. A computer system for delivering content such as still images, moving images, 3D images, animations, videos, and music by e-mail via a communication network,
A transmitting-side user terminal device for transmitting the electronic mail and the content by a transmitting-side user,
A mail server for receiving the e-mail from the sending user and delivering the e-mail to the receiving user;
A content distribution server for distributing the content,
A receiving user terminal device for the receiving user to receive the e-mail and the content,
The transmitting-side user terminal device generates a unique identification code for each e-mail to be transmitted, and generates header information obtained by encoding information including at least the identification code and the destination of the e-mail based on a specific algorithm. Header information generating means for generating, and mail transmitting means for transmitting a hypertext e-mail including the header information and the link information to the content distribution server to a mail server,
The mail server has a mail distribution unit that distributes a hypertext e-mail including the header information and the link information to the content distribution server from the transmission-side user terminal device to a reception-side user terminal device,
The content delivery server, content delivery means for delivering the content to the receiving user terminal device by being called from the hypertext of the email,
Content processing program transmitting means for transmitting a processing program for receiving and reproducing the content at the receiving user terminal device,
The receiving-side user terminal device receives an e-mail transmitted from the mail server, and decodes header information encoded based on a specific algorithm included in the e-mail to obtain necessary information. Header information acquisition means,
Link management means for managing whether or not to link to a content distribution server based on the header information obtained by the header information acquisition means and the hypertext link information of the electronic mail;
Content receiving means for performing a link by the link management means and receiving content from the content distribution server,
Content processing program receiving means for receiving a processing program for receiving and reproducing content from the content distribution server,
An e-mail system comprising: a content reproducing unit that receives and reproduces the content according to the content processing program. The content distribution server includes domain information embedding means for embedding domain information of the distribution server in the content, and the receiving-side user terminal device transmits the domain information embedded in the content to the content server. 3. The e-mail system according to claim 1, further comprising a domain information matching unit that checks the domain of the original content distribution server to identify illegal distribution. The method according to claim 1 or 2, wherein the header information decoding algorithm is supplied to the recipient-side user terminal device as hypertext information of an electronic mail or as an attached file of the electronic mail. 2. The e-mail system according to 2. The link management program to the content distribution server in the link management means is included in a decoding algorithm of the header information of the e-mail, is supplied as hypertext information of the e-mail, or is supplied as an attached file of the e-mail. The electronic mail system according to claim 1, wherein the electronic mail system is any one of: 3. The electronic mail system according to claim 1, wherein the content delivered by the electronic mail is a three-dimensional animation by a computer graphic corresponding to an HTML browser that can be interactively operated by a receiving user. 4. . The content processing program for receiving the content from the content distribution server and reproducing the content on the receiving user terminal device is a Java (R) applet called by hypertext link information of an electronic mail. The electronic mail system according to claim 1 or 2.

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