System for broadcasting electronic mails that separately stores and sends a portion of electronic mails with an access code for filtering and retrieving purpose

A broadcast communication system in which a terminal unit for sending electronic mail transmits electronic mail data containing text of electronic mail, transmission destination data, a first command indicative of a transmission condition and a second command indicating that broadcast distribution is to be conducted, a mail server, upon reception of electronic mail data containing a second command, transmits a title and an access code of electronic mail text to all of terminal units of transmission destinations indicated by transmission destination data and upon reception of electronic mail data not containing a second command, sends back electronic mail text corresponding to the access code, and a terminal unit for receiving electronic mail, at the time of reception of distribution of electronic mail text, transmits electronic mail data containing an access code to the mail server.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a broadcast communication system for
 distributing electronic mail to a plurality of specific subscribers over
 networks such as an internet and a local area network (LAN) and an
 electronic mail distribution method thereof.
 2. Description of the Related Art
 As a mode of using electronic mail by which data and messages are sent or
 received to/from a plurality of computer systems such as a personal
 computer and a workstation connected through a network, there is broadcast
 communication which distributes electronic mail to a plurality of specific
 subscribers at a time. In recent years, with the development of a public
 wide area network (WAN) such as an internet, use of broadcast
 communication by means of electronic mail has been sharply rising.
 Conventionally employed for a broadcast communication system using
 electronic mail of this kind are an electronic mail system shown in FIG. 6
 and a mail server shown in FIG. 7. FIG. 6 is a schematic diagram showing
 structure of an electronic mail system, while FIG. 7 is a block diagram
 showing structure of a conventional mail server which realizes an
 electronic mail system.
 The electronic mail system shown in FIG. 6 has a mail server 600, a sending
 station 740 for sending electronic mail and a plurality of accepting
 stations 750 for receiving electronic mail connected with each other over
 a network. In the illustrated example, the mail server 600, the sending
 station 740 and each accepting station 750 are respectively connected to
 individual networks 231, 232 and 233 which are connected to an internet
 210 through access points 221, 222 and 223, respectively. This arrangement
 enables transmission of electronic mail from the sending station 740 to
 each accepting station 750. Although the sending station 740 for sending
 electronic mail and the accepting station 750 for receiving electronic
 mail are separated from each other for the explanation's sake, they have
 no difference in structure as a terminal unit and function as the sending
 station 740 when individual terminal units connected to the network send
 electronic mail and function as the accepting station 750 when they
 receive electronic mail. Also in the illustrated example, although the
 mail server 600 and the terminal units 740 and 750 are connected to a
 plurality of networks connected to each other over the internet 210,
 networks can take any form and even with a simple WAN or LAN not connected
 to the internet 210, basic structure of an electronic mail system
 including the mail server 600, the terminal units 740 and 750 remains the
 same.
 With reference to FIG. 7, the mail server 600 includes an input/output
 interface 610, an input unit 620 and an output unit 630 for sending and
 receiving electric mail and other data to and from a network 231, a
 storage unit 640 for storing electronic mail, a command processing unit
 650 for conducting various processing for the distribution of electronic
 mail, and a control unit 660 for controlling operation of each of these
 function execution units.
 In thus structured electronic mail system, a user who intends to send
 electronic mail (hereinafter referred to as sender) sends a set of mail
 data containing a main body (text) of electronic mail which is a main
 portion of the electronic mail, transmission destination data indicating a
 destination of electronic mail, and a transmission command indicative of
 an electronic mail distribution condition from the terminal units 740 to
 the mail server 600. Mail data applied to the input/output interface 610
 of the mail server 600 through the network 231 is transferred to the input
 unit 620 by the instruction from the control unit 660. Then, of the mail
 data in question, the electronic mail main body and the transmission
 destination data are transferred to the storage unit 640 and stored at a
 predetermined position. The transmission command is transferred to the
 command processing unit 650.
 Next, the command processing unit 650 analyzes the received transmission
 command and in accordance with the instruction of the transmission
 command, instructs the storage unit 640 to retrieve and output an
 electronic mail main body and transmission destination data. The storage
 unit 640 transfers the electronic mail main body and the transmission
 destination data to the output unit 630 in accordance with the instruction
 from the command processing unit 650. The output unit 630 sends the
 electronic mail main body in question to the accepting station 750 used by
 a predetermined user (hereinafter referred to as receiver) in accordance
 with the transmission destination data in question.
 In the foregoing processing, designating a plurality of receivers as
 transmission destination data leads to realization of broadcast
 communication by means of electronic mail. Depending on the contents of a
 transmission command, a main body of electronic mail in question may be
 held in a mail box assigned to a receiver in the storage unit 640 in
 accordance with instructions from the command processing unit 650 and the
 control unit 660 and be transmitted in response to access made by the
 receiver in question by means of electronic mail.
 In the above-described broadcast communication using electronic mail,
 increase in the number of subscribers to service as a party to which
 electronic mail is sent results in concentration of enormous traffic on a
 network (the network 231 in the example shown in FIG. 6) to which the mail
 server connects. This adversely affects throughput of other terminal units
 connected to the network in question.
 In addition, there is a case where information of broadcast-communicated
 electronic mail is unnecessary temporarily or for a long period of time
 for reasons of a subscriber to service. In this case, sending electronic
 mail to the subscriber to the service in question results in wasteful use
 of network resources to deteriorate efficiency.
 One of conventional art intended to efficiently use a network line while
 avoiding such situations as mentioned above is, for example, a technique
 disclosed in Japanese Patent Laying-Open (Kokai) No. Heisei 64-11442,
 entitled "Electronic Mail Communication Control Method". The literature
 recites a communication control method aimed at reducing contentions among
 sending stations by divisionally managing electronic mail as a main body
 of electronic mail and a header part, notifying an accepting station of a
 header part prior to transmission of an electronic mail main body and
 preengaging transmission time of an electronic mail main body.
 While the communication control method disclosed in the above literature
 enables prevention of congestion in terms of time at the transmission of
 electronic mail, the method is still premised that a main body of mail is
 sent to all terminal units. This is because no means is provided for
 determining at an accepting station whether information of electronic mail
 is necessary for a subscriber to service. This disables avoidance of
 wasteful use of a network line caused by the transmission of electronic
 mail also to a terminal unit of a subscriber to service who needs no
 information of the electronic mail.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide a broadcast communication
 system which enables prevention of enormous traffic at a network caused by
 distribution of electronic mail by transmitting a predetermined
 notification of small data size to an accepting station prior to
 transmission of a main body of electronic mail, and an electronic mail
 distribution method thereof.
 Another object of the present invention, in addition to the above object,
 is to provide a broadcast communication system enabling efficient use of a
 network line by transmitting a main body of electronic mail only to a
 subscriber to service who wants reception of the electronic mail, and an
 electronic mail distribution method thereof.
 According to the first aspect of the invention, a broadcast communication
 system for distributing electronic mail to a plurality of subscribers to
 service at a time by means of an electronic mail system, comprises
 a mail server and a first and second terminal units connected with each
 other over a network, wherein
 the first terminal unit for sending electronic mail,
 sends electronic mail containing at least body of electronic mail,
 transmission destination data indicative of a transmission destination of
 the electronic mail, a first command indicative of a transmission
 condition of the electronic mail and a second command indicating that the
 electronic mail is to be broadcast-distributed,
 the mail server
 upon reception of the electronic mail containing the second command,
 transmits a title of the body of the electronic mail and an access code
 for accessing the body of the electronic mail to all of the second
 terminal units as transmission destinations indicated by the transmission
 destination data contained in the electronic mail, and
 upon reception of request for the body of the electronic mail, transmits
 the body of the electronic mail corresponding to the access code back to
 the second terminal unit which has transmitted the request for the body of
 the electronic mail, and
 the second terminal unit for receiving the electronic mail,
 upon reception of the title and the access code from the mail server, for
 receiving distribution of the body of the electronic mail corresponding to
 the title and the access code, transmits electronic mail containing the
 access code to the mail server.
 In the preferred construction, the second terminal unit transmits
 electronic mail containing not the second command but the access code to
 the mail server as the request for the body of the electronic mail.
 In the preferred construction, the first terminal unit produces the title
 of the body of the electronic mail body to be transmitted and the access
 code, adds the title and the access code to corresponding the electronic
 mail and transmits the electronic mail.
 In the preferred construction, the mail server, upon reception of the
 electronic mail containing the second command, produces, based on the body
 of the electronic mail, the title of the body of the electronic mail and
 the access code and adds the title and the access code to the electronic
 mail.
 In another preferred construction, the contents of the title of the
 electronic mail include an excerpt of the body of the electronic mail.
 Also, the second command is included in the first command.
 According to the second aspect of the invention, an electronic mail
 distribution method of conducting broadcast communication for distributing
 electronic mail to a plurality of subscribers to service at a time by
 means of an electronic mail system including a mail server and a first and
 second terminal units connected with each other over a network, comprising
 the steps of
 in the first terminal unit for sending electronic mail,
 producing electronic mail containing body of electronic mail, a title of
 the body of the electronic mail, transmission destination data indicative
 of a transmission destination of the electronic mail, a first command
 indicative of a transmission condition of the mail, a second command
 indicating that the mail is to be broadcast-distributed and an access code
 for accessing the body of the electronic mail, and
 transmitting the electronic mail produced to the mail server,
 in the mail server, checking whether received electronic mail contains the
 second command,
 upon detection of the second command, transmitting the title of the body of
 the electronic mail and the access code contained in the electronic mail
 to all of the second terminal units of transmission destinations indicated
 by the transmission destination data contained in the electronic mail,
 upon detection of none of the second command, checking whether the access
 code is contained in the electronic mail, and
 upon detection of the access code, transmitting the body of the electronic
 mail corresponding to the access code detected to the terminal unit which
 has sent the electronic mail,
 in the second terminal unit for receiving the electronic mail,
 upon reception of the title and the access code from the mail server,
 transmitting electronic mail containing the access code to the mail server
 according to indication of receiving distribution of the boy of the
 electronic mail from a user.
 In the preferred construction, in the second terminal unit, further
 including a step of urging a user to determine whether to receive
 distribution of the body of the electronic mail corresponding to the title
 and access code received, upon reception of the title and the access code
 from the mail server.
 In the preferred construction, in the first terminal unit, the electronic
 mail data producing step comprises
 at the production of the transmission destination data, checking whether a
 transmission destination of the electronic mail is registered at the mail
 server,
 when the transmission destination is registered at the mail server,
 selecting the registered code as the transmission destination data, and
 when the transmission destination is not registered at the mail server,
 producing a list of transmission destinations as the transmission
 destination data.
 According to another aspect of the invention, a computer readable memory
 storing a computer program for conducting broadcast communication for
 distributing electronic mail to a plurality of subscribers to service at a
 time by means of an electronic mail system including a mail server and a
 plurality of terminal units connected with each other over a network, the
 computer program comprising the steps of
 in the first terminal unit for sending electronic mail
 producing electronic mail containing body of electronic mail, a title of
 the body of the electronic mail, transmission destination data indicative
 of a transmission destination of the electronic mail, a first command
 indicative of a transmission condition of the mail, a second command
 indicating that the mail is to be broadcast-distributed and an access code
 for accessing the body of the electronic mail, and
 transmitting the electronic mail produced to the mail server,
 in the mail server,
 checking whether received electronic mail contains the second command,
 upon detection of the second command, transmitting the title of the body of
 the electronic mail and the access code contained in the electronic mail
 to all of the second terminal units of transmission destinations indicated
 by the transmission destination data contained in the electronic mail,
 upon detection of none of the second command, checking whether the access
 code is contained in the electronic mail, and
 upon detection of the access code, transmitting the body of the electronic
 mail corresponding to the access code detected to the terminal unit which
 has sent the electronic mail,
 in the second terminal unit for receiving the electronic mail,
 upon reception of the title and the access code from the mail server,
 transmitting electronic mail containing the access code to the mail server
 according to indication of receiving distribution of the boy of the
 electronic mail from a user.
 Other objects, features and advantages of the present invention will become
 clear from the detailed description given herebelow.

DESCRIPTION OF THE PREFERRED EMBODIMENT
 The preferred embodiment of the present invention will be discussed
 hereinafter in detail with reference to the accompanying drawings. In the
 following description, numerous specific details are set forth in order to
 provide a thorough understanding of the present invention. It will be
 obvious, however, to those skilled in the art that the present invention
 may be practiced without these specific details. In other instance,
 well-known structures are not shown in detail in order to unnecessary
 obscure the present invention.
 FIG. 1 is a schematic diagram showing structure of an electronic mail
 system which realizes a broadcast communication system using electronic
 mail according to one embodiment of the present invention, while FIG. 2 is
 a block diagram showing structure of a mail server in the present
 embodiment. In FIGS. 1 and 2, illustration is made only of a
 characteristic part of the structure of the present embodiment and that of
 the remaining common part is omitted.
 As shown in FIG. 1, the electronic mail system realizing a broadcast
 communication system according to the present embodiment is the same in
 basic structure as a conventional electronic mail system. More
 specifically, the electronic mail system has a mail server 100, a sending
 terminal 240 for sending electronic mail and a plurality of accepting
 stations 250 for receiving electronic mail connected with each other over
 a network. In the present embodiment, the mail server 100, the sending
 station 240 and the accepting station 250 are implemented by a computer
 system such as a personal computer or a workstation. Although the sending
 station 240 for sending electronic mail and the accepting station 250 for
 receiving electronic mail are separated from each other for the
 explanation's sake, they have no difference in structure as a terminal
 unit and function as the sending station 240 when individual terminal
 units connected to the network send electronic mail and function as the
 accepting station 250 when they receive electronic mail. Also in the
 illustrated example, although the mail server 100 and the terminal units
 240 and 250 are connected to a plurality of networks connected to each
 other over the internet 210, networks can take any form and even with a
 simple WAN or LAN not connected to the internet 210, basic structure of an
 electronic mail system including the mail server 100 and the terminal
 units 240 and 250 remains the same. In addition, it is clearly understood
 that although in FIG. 1, a total of three terminal units 240 and 250 are
 illustrated, the number of terminal units is not limited to that shown in
 the figure.
 With reference to FIG. 2, the mail server 100 includes an input/output
 interface 110, an input unit 120 and an output unit 130 for sending and
 receiving electric mail and other data to and from the network 231, a
 storage unit 140 for storing electronic mail, a command processing unit
 150 for conducting various processing for distributing electronic mail,
 and a control unit 160 for controlling operation of each of these function
 execution units.
 In above-described structure, the storage unit 140, which is implemented by
 an external storage device such as a magnetic disk device or an internal
 memory such as an RAM, includes an electronic mail main body storage unit
 141 for storing a main body of electronic mail which is a main portion
 (text) of the electronic mail, a title storage unit 142 for storing a
 title of electronic mail, an access code storage unit 143 for storing an
 access code as a key for access to the electronic mail in question, and a
 transmission destination address storage unit 144 for storing transmission
 destination data indicating a destination of electronic mail.
 The control unit 160 is implemented by program-controlled CPU and internal
 memory such as an RAM. A control program which controls the CPU is stored
 in a storage medium 170 for provision and loaded into the control unit 160
 to conduct control of the above-described function execution units.
 Applicable as the storage medium 170 is a common storage medium such as a
 magnetic disk, an optical disk or a semiconductor memory.
 Next, with reference to FIGS. 1 and 2 and flow charts of FIGS. 3 to 5,
 description will be made of operation of the present embodiment with
 respect to an example in which the sending station 240 distributes
 electronic mail by broadcast communication to the two accepting stations
 250 shown in FIG. 1 through the mail server 100. FIG. 3 is a flow chart
 showing operation to be conducted when the sending station 240
 broadcast-distributes electronic mail, FIG. 4 is a flow chart showing
 operation of the mail server 100 and FIG. 5 is a flow chart showing
 operation of the accepting station 250.
 Operation of the sending station 240 will be described. With reference to
 FIG. 3, when electronic mail to be broadcast-distributed is generated at
 the sending station 240 (Step 301), the sending station 240 first produces
 an access code related to a main body of the electronic mail in question
 (Step 302). When a distribution destination of the electronic mail is
 registered at the mail server 100 in advance, the station 240 selects the
 registered distribution destination code as transmission destination data
 of the electronic mail in question (Steps 303 and 304). On the other hand,
 when a distribution destination of the electronic mail in question is not
 registered at the mail server 100, the station 240 produces a distribution
 destination list as transmission destination data (Steps 303 and 305).
 Next, the station 240 sends a set of mail data containing a main body of
 the electronic mail, a title of the electronic mail, an access code,
 transmission destination data and a transmission command to the mail
 server 100 (Step 306). For conducting broadcast distribution, a command
 indicating that the mail is to be broadcast-communicated is added to the
 mail data. This command may be added, for example, as a transmission
 command indicative of a transmission condition.
 Title of electronic mail contained in mail data may include only a header
 of a main body of the electronic mail or also include an excerpt of the
 contents of the electronic mail main body. Although in the above-described
 operation example, a title and an access code are assumed to be produced
 at the sending station 240, they may be produced at the mail server 100
 under control of the control unit 160.
 Next, operation of the mail server 100 upon reception of electronic mail
 instructing on broadcast mail distribution will be described. When at the
 mail server 100, the input/output interface 110 receives mail data from
 the network 111 (Step 401), the mail data is transferred to the input unit
 120 by the instruction from the control unit 160 (Step 402). The input
 unit 120 searches the received mail data for a command indicative of
 broadcast distribution (Step 403). Upon detecting a command indicative of
 broadcast distribution, the input unit 120 extracts a transmission command
 from the mail data and transfers the same to the command processing unit
 150 (Steps 404 and 405). The unit 120 also transfers other data than the
 transmission command to the storage unit 140 (Steps 404 and 407).
 The command processing unit 150 analyzes the received transmission command
 in question (Step 406). The storage unit 140 classifies the received data
 to store a main body of the electronic mail in the electronic mail main
 body storage unit 141, a title of the electronic mail in the title storage
 unit 142, an access code in the access code storage unit 143 and
 transmission destination data in the transmission destination address
 storage unit 144 (Step 408).
 After analyzing the transmission command under control of the control unit
 160, the command processing unit 150 reads a title, an access code and
 transmission destination data indicated by the analysis result from the
 storage unit 140 (Step 409) and transfers the same to the output unit 130
 (Step 410). The output unit 130 sends a pair of received title and access
 code as a reception notification to the accepting station 250 of every
 receiver indicated by the transmission destination data (Step 411).
 When at Step 403, no command indicative of broadcast distribution is
 detected, determination is made whether it is access from a subscriber to
 the service or not (Step 412) and when it is the access from a subscriber
 to the service, check is made whether an access code is contained in the
 mail data in question or not (Step 413). When it is not access from a
 subscriber to the service, or when no access code is contained in the mail
 data, appropriate error processing such as return of an error message is
 conducted to finish the routine.
 When an access code is contained in the mail data, an electronic mail main
 body corresponding to the access code is read from the electronic mail
 main body storage unit 141 at the storage unit 140 and transferred to the
 output unit 130 under control of the control unit 160 (Step 414). The
 output unit 130 sends the received main body of the electronic mail to the
 accepting station 250 of the subscriber to the service who has made access
 (Step 415).
 Depending on the contents of a transmission command or a control program of
 the control unit 160, it is possible to hold a title and an access code of
 electronic mail in pairs in a mail box of each subscriber to the service
 provided at the storage unit 140 to distribute a reception notification
 containing the tile and the access code in response to access by
 electronic mail from a subscriber to the service.
 Description will be next made of operation of the accepting station which
 has received a set of a title and an access code. Upon receiving a
 reception notification containing a title and an access code of electronic
 mail (Step 501), the accepting station 250 outputs and displays the
 contents of the reception notification to wait for determination to be
 made by a subscriber to the service as a user. The subscriber to the
 service in question refers to the title of the electronic mail displayed
 on the accepting station 250 to determine whether to receive the
 electronic mail in question or not (Step 502). For receiving the
 electronic mail in question, the station 250 sends back electronic mail
 for request of the electronic mail main body containing the access code
 contained in the reception notification to the mail server 100 (Step 503).
 The mail server 100 having received the return mail sends the main body of
 the electronic mail to the accepting station 250 following the procedure
 shown at Steps 412 to 415 of FIG. 4. Then, the accepting station 250
 receives the main body of the electronic mail in question to complete the
 processing (Step 504).
 When the subscriber to the service determines at Step 502 that the
 electronic mail in question is unnecessary, the accepting station finishes
 the processing without returning mail to the mail server 100.
 As described in the foregoing, by first sending only a title and an access
 code of electronic mail, the broadcast communication system of the present
 embodiment and the electronic mail distribution method thereof achieve
 more drastic reduction in the amount of data transmitted than that
 achieved by a conventional distribution method in which a main body of
 electronic mail is sent to all terminal units. This prevents enormous
 traffic from concentrating on a part of a network at the time of data
 transmission.
 In addition, sending a main body of electronic mail only to a subscriber to
 service who wants to receive the electronic mail enables more efficient
 use of a network line than that by a conventional distribution method in
 which a main body of electronic mail is sent to all terminal units
 irrespective of intention of subscribers to the service.
 Although the invention has been illustrated and described with respect to
 exemplary embodiment thereof, it should be understood by those skilled in
 the art that the foregoing and various other changes, omissions and
 additions may be made therein and thereto, without departing from the
 spirit and scope of the present invention. Therefore, the present
 invention should not be understood as limited to the specific embodiment
 set out above but to include all possible embodiments which can be
 embodies within a scope encompassed and equivalents thereof with respect
 to the feature set out in the appended claims.