Abstract:
The present invention relates to a mail server for a network. The mail server has a sender part arranged to receive outgoing e-mails from users of the network and to send the received e-mails to their recipients. The sending part is arranged to copy at least some of the contents in the received e-mail to a storage. The sending part provides an amended e-mail based on the received e-mail, said amended e-mail comprising at least one pointer substituting the contents copied to the storage, said pointer pointing at said contents in said storage.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to e-mail communication. In particular, it concerns a mail server for a private or public network. 
         [0002]    It also relates to a network comprising said mail server and a method for sending e-mail in such network. 
       BACKGROUND 
       [0003]    E-mail communication is today a widely spread communication means. It provides an important tool in the daily work in many businesses. The amount of e-mails that are sent is steadily increasing. However, the increased amounts of e-mails which are handled by company mail servers and by workers within companies cause problems. For example, it has been reported decreasing effectiveness of employees in companies, if the mail server is down. Further, mail boxes of the users have usually a limited size. When the size of the mail box has been exceeded, e-mail traffic can be stopped. This causes heavy inconveniences for the user. This can also be very frustrating. The user has no control over the size of the inbox, as he/she has no control over the amount of e-mails received and the size of the received e-mails. 
         [0004]    Further, privacy is weak, since the e-mails are generally not encrypted. 
       SUMMARY 
       [0005]    One object of the present invention is to solve at least some of the problems mentioned above. 
         [0006]    This has been achieved by means of an improved mail server for a network. The mail server has a sender part arranged to receive outgoing e-mails from users of the network and to send the received e-mails to their recipients. The sender part is further arranged to copy at least some of the contents in the e-mail to a storage and to provide an amended e-mail based on the e-mail, said amended e-mail comprising at least one pointer substituting the contents copied to the storage, said pointer pointing at said contents in said storage. Thereafter, the amended e-mail is sent to the recipient. 
         [0007]    One advantage of the mail server described above is that the recipients gain better control over the size of their inboxes, as the substantial contents of the received e-mails are still stored at the sender&#39;s site. The receiver does not download the contents to his/her own computer until he/she activates the pointer. Further, the business case of sending spam attachments will be reduced since the sender is keeping the contents. 
         [0008]    In accordance with one embodiment, the pointer is an address to data managed by a web server, a so called URL. Communication with said address can be encrypted with HTTPS. Thereby the contents stored at the storage server can be transmitted to the recipient over an encrypted tunnel. The term HTTPS indicates a secure HTTP connection. 
         [0009]    In accordance with one embodiment, the sender part is arranged to sign, and possibly also encrypt the amended e-mail. The amended e-mail is for example signed with a private key associated to the sender part. The encryption is for example performed using a public key associated to the recipient of the e-mail. 
         [0010]    The contents copied to the storage comprises in one example one or a plurality of attachments. Further, the sender part can be arranged to copy the received outgoing e-mail itself with at least some of its contents to the storage. Further, the contents copied to the storage server can be encrypted for example using a key associated to the recipient 
         [0011]    The mail server is usually also arranged to receive incoming e-mails. Accordingly, it has a receiver part arranged to receive incoming e-mails and to forward the incoming e-mails to their recipients present in a private or public network served by said mail server. 
         [0012]    In one example, the receiver part is arranged to amend the pointer in the received e-mail so as to point at its destination via a proxy server associated with the mail server. If the communication is based on HTTPS, a secure tunnel can thereby be provided between a storage at the sender side and the proxy server. The contents at the tunnel endpoint in the storage can thereby be downloaded to the proxy server through the secure connection. If the contents are an e-mail, the proxy server can then forward the e-mail to the mail server for further transmittal to the recipient. 
         [0013]    The receiving part can be arranged to verify the mail server from which an incoming e-mail originates and to, if the originating server is verified, amend the pointer in the received e-mail so as to point at its destination via the proxy server associated with the mail server. 
         [0014]    The present invention also relates to a network comprising a mail server and a plurality of clients served by said mail server, wherein the mail server has a sender part in accordance with the above and storage in accordance with the above. 
         [0015]    The present invention further relates to a network comprising a mail server, a plurality of clients served by said mail server, and a proxy server. The mail server has a receiving part arranged to receive incoming e-mails and to send the received e-mails to their recipients within the network. The proxy server is arranged to amend a pointer in the received e-mail so that the pointer points at its destination via the proxy server. Communication is for example encrypted with HTTPS, in which case the amended pointer defines the proxy server as one of the channel endpoints for HTTPS. 
         [0016]    The invention further relates to a method for sending e-mails from users in a network and a method for receiving e-mails. Said methods have features corresponding to those described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a block scheme over a first private or public network and a second private network in communication over the Internet. 
           [0018]      FIG. 2  is a block scheme over a personal computer in one of the private or public networks in  FIG. 1 . 
           [0019]      FIG. 3  is a flow chart illustrating the operation of a mail server in the first (sending) private or public network in  FIG. 1 . 
           [0020]      FIG. 4  is a flow chart illustrating an example of the operation in the second (receiving) private or public network when e-mails are stored on the storage server of  FIG. 1 . 
           [0021]      FIG. 5  is a flow chart illustrating an example of the operation in the second (receiving) private or public network when attachments are stored on the storage server of  FIG. 1 . 
           [0022]      FIG. 6  is a bock scheme showing an example of a sending part in at least one of the mail servers in  FIG. 1 . 
           [0023]      FIG. 7  is a block scheme showing an example of the storage server in  FIG. 1 . 
           [0024]      FIG. 8  is a bock scheme showing an example of a receiving part in at least one of the mail servers in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    In  FIG. 1 , a number of personal computers  102   a ,  102   b ,  102   c ,  102   d  in a first private network  101 , for example a company or Internet Service Provider network, are connected to a first mail server  103 . The communication between the personal computers  102   a ,  102   b ,  102   c ,  102   d  and the first mail server  103  takes place for example using SMTP (Simple Mail Transfer Protocol). The first mail server  103  is associated with a storage sever  104  of the first private network  101 . Both the first mail server  103  and the storage server  104  of the first private network  101  are available to the Internet  105 . 
         [0026]    A number of personal computers  102   e ,  102   f ,  102   g ,  102   h  in a second private network  106 , for example a company network, are associated with a second mail server  107 . The communication between the personal computers  102   e ,  102   f ,  102   g ,  102   h  of the second private network  106  and the second mail server  107  takes place for example using POP3 (Post Office Protocol version 3). The second mail server  107  is associated with an e-mail storage proxy server  108  of the second private network  106 . Both the second mail server  107  and the e-mail storage proxy server  108  are available to the Internet  105 . Thus, data can be communicated between the first mail server  103  and storage server  104  of the first network  101  and the second mail server  107  and e-mail storage proxy server  108  of the second network  106  over the Internet  105 . 
         [0027]    In the herein described example based on use of a public and private key (PKI), both the first and second networks  101 ,  106  are in communication with one or a plurality of key servers  109 . The key servers  109  are arranged to store the public keys of the users in the networks  101 ,  106 . In one example, the first and second mail servers  103 ,  107  of the first and second networks  101 ,  106  are arranged to provide the user&#39;s public keys to the key server  109 . In another example, the users themselves provide their public keys to the key server  109 . 
         [0028]    In this description, operations and means for sending e-mails are described in relation to the first network  101  and operations and means for receiving e-mails are described in relation to the second network  106 . In practice, both networks have usually means for both sending and receiving e-mails in the herein described manner. 
         [0029]    In  FIG. 2 , the personal computers  202  of the first and second networks  101 ,  106  are provided with means  210  for e-mail correspondence. The means for e-mail correspondence comprises in one example software arranged to support inclusion of attachment files in the e-mails. In one example, Microsoft Outlook or other commercially available software for e-mailing is installed on, or accessible by, the personal computers  202 . The personal computers  202  are associated to one or a plurality of users. In one example, each user has a private key  211  on his/her personal computer. Accordingly, e-mails produced by the user on his/her computer can be digitally signed with the private key of that user. The signing is performed when the e-mail is sent. The public keys are stored in the key server  109 , as described above in relation to  FIG. 1 . 
         [0030]    In  FIG. 3 , the first mail server  103 , acting as sender of e-mails in the herein described example, is arranged to receive e-mails in a step  312  from the personal computers  102   a ,  102   b ,  102   c ,  102   d  of the first private network  101 . In the shown example, the first mail server  103  is arranged to verify the identity of the user in a step  313  before processing the incoming mail further. In one example, wherein the received e-mail is signed with the private key of the user who sent the e-mail, the verification is accomplished using the user&#39;s public key for authentication of the user in known manner. In this example, the first mail server  103  has stored thereon or access to public keys of the users of the first network. The first mail server  103  is then arranged to process the received e-mails before transmittal to the recipient. 
         [0031]    Accordingly, the first mail server  103  is arranged to determine whether the received e-mail is to be directly sent to the recipient or modified before transmittal in a step  314 . In one example, the determination is based on the size of the received e-mail. Accordingly, if the e-mail exceeds a predetermined size, then the e-mail is modified in the manner described below before transmittal. If on the other hand, the mail size is smaller than the predetermined size, the e-mail is possibly encrypted in a step  319  and thereafter sent directly to the recipient in a step  321 . In another example, the determination is based on the presence of attachments in the mail. Accordingly, if the e-mail comprises one or more attachments, then the e-mail is modified in the manner described below before transmittal. If on the other hand, the e-mail does not comprise any attachments, the e-mail is possible encrypted in the step  319  and thereafter sent to the recipient in the step  321 . The determination can be based on a number of other parameters such as the identity of the sender and/or receiver of the e-mail. The encryption step  319  of the e-mail is in one example performed using a public key of the final recipient of the e-mail (the recipient user). The public key of the recipient user is available by means of the key server  109 . 
         [0032]    If it is determined in the step  314  that the e-mail is to be sent directly to the recipient in the step  321 , possibly encrypted in the step  319 , the mail server is arranged to send the email further to the recipient without any modifications. The e-mail is in one example sent by SMTP e-mail transport over the Internet. 
         [0033]    If it is determined that the e-mail is to be modified, the first mail server  103  is arranged to perform at least some of the steps described in the following with reference to  FIG. 3 . 
         [0034]    In the herein described example, the first mail server  103  is arranged to provide a copy of the received and verified e-mail in a step  315 . The received and verified e-mail comprises in one example no attachments. In another example, it comprises one or a plurality of attachments. Irrespective of which, the mail server is in one example arranged to encrypt the copy of the e-mail in a step  316 . The copy of the e-mail is for example encrypted in the encryption step  316  with the public key of the recipient user. The public key can be provided from the key server described above. The first mail server  103  is arranged to feed the encrypted e-mail copy to the storage server  104  in a step  317 . In an alternative example, the first mail server  103  is not arranged to perform the encryption step  316  so as to encrypt the copy before feeding it to the storage server  104 . The storage server  104  can then be arranged to encrypt the copy for example using the public key of the recipient user. 
         [0035]    Thus, the copy of the e-mail is stored on the storage server  104  substantially in its original format encrypted with the public key of the recipient user. If the e-mail has been signed by the sending user using a certificate-based method, the signature is in one example not removed from the copy of the e-mail, stored at the storage server. Then, the sender and contents of the e-mail copy can be verified by the recipient user. The storage server  104  is in one example arranged to remove e-mails stored thereon based on preset criteria. In one example, the storage server is arranged to remove e-mails which have been stored thereon for a predetermined time period. 
         [0036]    The first mail server  103  is further arranged to provide an amended version of the received e-mail for transmittal to the recipient. In the shown example, the mail server is arranged to perform amendments in a first amendment step  318  of the incoming e-mail related to the contents of the e-mail. In one example, the amendment involves a step  318   a  of removing all contents from the e-mail (attachments and text written by the sender). In another example the amendment involves a step  318   a  of removing some of the contents from the e-mail, e.g. all attachments or all attachments of a predetermined format (such as pdf). The first mail server  103  is further arranged to create a pointer to the copy of the original mail stored on the storage server  104  in a step  318   b . The pointer is then included in the amended e-mail. The pointer is for example a web server address, a so called URL. In one example, communication with said web server address he is based on encryption with HTTPS. The amendment comprises in one example further including information related to the removed subject matter in the amended e-mail. For example information related to attachments comprised in the original e-mail can be included. The information includes for example file size, creation date, file name, author etc. 
         [0037]    In one example, the first mail server  103  is arranged to perform the amendment step  318  by removal and addition of information in the originally received mail. In an alternative example, the amendment is performed by creating a new e-mail. Relevant parts of the original mail are then copied into the created mail and the new information (as described above) is entered into the e-mail. 
         [0038]    In the shown example, the first mail server  103  is arranged to perform amendments of the incoming e-mail so as to be identifiable to the second mail server  107  of the second private network. Accordingly, in one example amendments are performed related to the identity of the sender in a second amendment step  320 . This amendment step  320  comprises in one example signing the amended e-mail with a private key associated to the first mail server  103 . The associated public key is in one example stored at the key server  109 . In another example, the first server  103  has sent the second mail server  107  its public key. 
         [0039]    The first mail server  103  is arranged to send the amended email further to the recipient&#39;s mail server in the sending step  321 . The e-mail is in one example sent by SMTP e-mail transport over the internet. In the example illustrated in  FIG. 3 , the e-mail is encrypted in the encryption step  319  before the amendments are performed related to the identity of the sender in the step  320 . The encryption step  319  for encryption of the e-mail is in one example performed using a public key of the final recipient of the e-mail (the recipient user). The public key of the recipient user is available by means of the key server  109 . 
         [0040]    The steps discussed above performed by the first mail server  103  are not necessarily performed in the above described order. 
         [0041]    In an alternative example, the first mail server  103  is not arranged to store a copy of the received e-mail on the storage server  104 . Instead, it is arranged to store attachments comprised in the received e-mail on the storage server. In this case, it is possible for the recipient to verify that the received e-mail was forwarded by the first mail server  103 . However, it is not possible for the recipient to verify the original sender of the attachment. The pointer described above, comprised in the modified e-mail, is in this alternative example arranged to point at an attachment in the storage server. Accordingly, if the original e-mail comprises a plurality of attachments, the amended mail comprises one pointer for each attachment. The attachments stored at the storage server is in one example encrypted with the public key of the recipient, as described in relation to the example described above, wherein the entire e-mail is stored on the storage server. In yet an alternative example, both the copy of the received e-mail (with or without included attachments, if any) and the attachments are stored on the storage server  104 . 
         [0042]    In the shown example in  FIG. 7  the storage server  104  is arranged to store both attachment files  738  and e-mails  739 . In an alternative example, the storage server  104  is arranged to store either attachment files  738  or e-mails  739 . 
         [0043]    In  FIG. 6 , a sending part  634  of the at least the first mail server  103  comprises a verification unit  635  arranged to perform the step  313  of verifying the user as described in relation to  FIG. 3 . The sending part comprises also a copying unit  636  arranged to perform the steps of providing a copy  315  and feeding  317  the copy to the storage server. The copying unit  636  may also be arranged to perform the step  315  so as to encrypt the copy. The sending part comprises also an e-mail processing unit  637  arranged to process the received e-mail in accordance with at least some of the steps  318 - 320  in  FIG. 3  so as to provide an amended e-mail for transmittal to the recipient. The units of the sending part  634  are to be seen as logical units which are implemented in software and/or hardware. 
         [0044]      FIG. 4  describes an example, wherein the storage server  104  is arranged to store a copy of the received e-mail (with or without attachments) on the storage server  104 . The second mail server  107 , serving the recipient, is arranged to receive e-mails for example over SMTP from the Internet in a step  422 . If the received e-mail is signed, the second mail server  107  is then arranged to verify the identity of the first mail server  103  from which the received e-mail was sent in a step  423 . Accordingly, the digital signature of the first mail server  103  is verified. In an example, wherein the received e-mail is signed based on a public and private key, the first mail server  103  is verified against a public key associated to the first mail server  103 . In one example, the second mail server is arranged to provide the public key for the first mail server  103  from the key server  109  available over the Internet. In another example, public keys have been exchanged between the mail servers  103 ,  107  of the associated first and second networks  101 ,  106 . If the identity of the mail server from which the received e-mail originates is verified, the second mail server  106  is arranged to forward the e-mail to the recipient in the manner described below. 
         [0045]    If the received and verified e-mail does not comprise a pointer, the receiving mail server  107  is arranged to forward the e-mail directly to the recipient in a step  432 . 
         [0046]    If, on the other hand, the received, and verified e-mail comprises a pointer, and if the contents at which the pointer points is an e-mail, the following steps are performed by the second network  106 . The second mail server  107  is arranged to modify the pointer in a step  424  so that it still points to the recipient user but through the secure e-mail storage proxy server  108  of the recipient&#39;s network  106 . The e-mail is then sent to the mail-box of the recipient user in a step  425 . The e-mail is sent using the same transport as is usually used in communication between the first and second mail servers  103 . In an alternative example (not illustrated), the computer of the recipient user is arranged to modify the pointer so that it points to the recipient user through the secure e-mail storage proxy server  108 . In accordance therewith, the second mail server  107  does not need to modify the pointer in the step  424  before sending it to the mail-box of the recipient user in the step  425 . 
         [0047]    As the pointer (URL) provides a link to the sender&#39;s storage server  104 , the recipient of the e-mail just has to click on the pointer. In response to that, communication between the recipient and the storage server  104  of the first private network  101  is started in steps  427 ,  428  via the storage proxy  108 . Thereby, the e-mail (with or without attachment(s)), at which the pointer points, can be downloaded to the computer of the recipient (or somewhere else in the recipient&#39;s network). If the e-mail at which the pointer points is encrypted, an encryption program of the recipient is arranged to decrypt in a step  430  the downloaded e-mail with his/her own private key. Further, the encryption program of the recipient is arranged to verify the digital certificate of the sender (user&#39;s certificate) associated to the downloaded e-mail in a step  431 . 
         [0048]    If the pointer in the received e-mail is encrypted with HTTPS, a secure tunnel is opened in a step  426 . The tunnel endpoints are the storage server  104  of the first network  101  and the proxy server  108  of the second network  106 . The tunnel endpoints are in known manner specified in a HTTPS certificate accessible to the storage server  104  and the proxy server  108 . The e-mail or attachment at which the pointer points, is then sent in a step  427  over the connection encrypted with HTTPS to the receiver&#39;s proxy server  108 . The proxy server  108  is then arranged to send the received e-mail in a step  428  to the second mail server  107 , which forwards the e-mail (including or not including attachment(s)) in a step  429  to the recipient. The encryption program of the recipient is arranged to decrypt the downloaded e-mail/attachment in a step  430  with his/her own private key. Further, the e-mail program of the recipient is arranged to verify the signature of the sender (a user of the first private network  106 ) associated to the downloaded e-mail in the step  431 . In order to enable decryption and verification, the personal computer  202  of  FIG. 2  comprises in one example means for decryption and verification. 
         [0049]    The operation of the recipient&#39;s network  106  is in  FIG. 4  described in relation to the herein described sender&#39;s network  101 . However, the recipient&#39;s network  106  herein described can cooperate with any storage server  104  arranged to store e-mails. In one example, the stored e-mails are signed with the signature of the sender and/or encrypted. The encryption is for example performed with a public key of the receiver. 
         [0050]    In  FIG. 8 , a receiving part  840  of the at least the first second mail server  107  comprises a verification unit  841  arranged to perform the step  423  of verifying the sender as described in relation to  FIG. 4 . The receiving part  842  comprises also a pointer amendment unit  842  arranged to perform the step  424  of modifying the pointer in  FIG. 4  before transmittal of the e-mail to the recipient. The units of the receiving part  840  are to be seen as logical units which are implemented in software and/or hardware. 
         [0051]      FIG. 5  describes an example, wherein the storage server  104  is arranged to store attachments on the storage server  104 . The receiving mail server  107  is arranged to forward the e-mail in a step  525  directly to the recipient irrespectively whether the received (step  522 ) and verified (step  523 ) e-mail comprises a pointer or not. As the pointer (URL) provides a link to the sender&#39;s storage server  104 , the recipient of the e-mail just has to click on the pointer. In response to that, communication between the recipient and the storage server  104  of the first private network  101  is started. Thereby, the attachment at which the pointer points, can be downloaded to the computer of the recipient (or somewhere else in the recipient&#39;s network) in a step  533 . If the pointer uses HTTPS, the downloading is performed in the encrypted tunnel provided by HTTPS in a step  526 . If the attachment itself is encrypted, an encryption program of the recipient is arranged to decrypt the downloaded attachment with his/her own private key in step  530 . Further, the encryption program of the recipient is in the illustrated example arranged to verify (step  531 ) the digital signature of the sender (user&#39;s certificate) associated to the downloaded attachment. 
         [0052]    In the description above, encryptions are performed using any encryption method based on the use of a public and private key (PKI). However, also other encryption methods can be used, for example those relying on storage of keys by a trusted part.