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Simultaneous access of different users to one mailbox by IMAP?

Last post 01-08-2020, 14:07 by Joerg. 9 replies.
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  •  01-07-2020, 15:37

    • Joerg is not online. Last active: 02-19-2020, 13:28 Joerg
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    Simultaneous access of different users to one mailbox by IMAP?

    We are maintaining (additionally to standard user mailboxes for each single user) different public mailboxes in our Pmail/Mercury network installation, where different users could simultaneously woking at. This works fine so far, but these special public mailboxes are not accessable via Mercury IMAP server, where you could subscribe only own (standard user) mailbox folders.

    The problem is, that we have to get access to these public folders also from remote, e.g. for home and street workers. Now we've got the thought to migrate the public folders with there single e-mail files back to a standard user mailbox, where users could get access via IMAP. We are already using Roundcube (Webmail GUI) for getting access to our mailboxes from remote via Mercury I. Works also fine.

    Now the question: Is it possible that different users have simultaneous access to one Pmail standard mailbox when accessing via IMAP? When accessing via Pmail the mailbox is being locked, but is the mailbox locked by IMAP as well? I darkly remember that this topic was already discussed in past, when users would like to get access via their iPhones and IMAP. Maybe anybody could state its experience whether this way works or not.


    Mercury 4.81.187 @Windows Server 2016, with 16-100 user licence
    Pegasus 4.73.639, network installation
  •  01-07-2020, 16:01

    • Brian Fluet is not online. Last active: 02-13-2020, 14:59 Brian Fluet
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    Re: Simultaneous access of different users to one mailbox by IMAP?

    Joerg,

     IMAP access locks the mailbox with a MAILBOXM.LCK file. 

    I don't have experience with multiple IMAP connections to the same mailbox directory but I do have users accessing a mailbox simultaneously via IMAP and local Pegasus Mail.  They have to override the lock warning thrown by Pegasus Mail.  Problems of corruption have occurred twice over several years so it's very rare.  I can't for certain that the simultaneous access was the cause of the corruption.


  •  01-07-2020, 16:29

    • Brian Fluet is not online. Last active: 02-13-2020, 14:59 Brian Fluet
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    Re: Simultaneous access of different users to one mailbox by IMAP?

    I forgot to mention that access by IMAP is blocked when the local Pegasus Mail lock is in place (MAILBOXP.LCK).  I suspect that a second IMAP connection attempt will be blocked when the Mercury lock is in place (MAILBOXM.LCK).
  •  01-07-2020, 16:45

    • Joerg is not online. Last active: 02-19-2020, 13:28 Joerg
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    AW: Re: Simultaneous access of different users to one mailbox by IMAP?

    Thanks Brian,

    I'm aware about the locks as far Pmail is using the mailbox. That's why we would try a simultaneous access to such a mailbox by different Thunderbirds or Roundcube via Mercury I, but never by using Pmail.


    Mercury 4.81.187 @Windows Server 2016, with 16-100 user licence
    Pegasus 4.73.639, network installation
  •  01-07-2020, 16:56

    • Joerg is not online. Last active: 02-19-2020, 13:28 Joerg
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    AW: Re: Simultaneous access of different users to one mailbox by IMAP?

    Just checked the access via two different Roundcube sessions. One has been started with Firefox, the other with Chrome browser. Both browsers are working on the same machine. I was able to access the same (my own) standard mailbox simultaneously from both Roundcube sessions, and was also able to open the same e-mail. After closing both Roundcube sessions I could start Pmail without any lock messages.

    I have to carry out some more tests, especially to check whether such simultaneous work makes the mail folders corrupt.


    Mercury 4.81.187 @Windows Server 2016, with 16-100 user licence
    Pegasus 4.73.639, network installation
  •  01-07-2020, 17:21

    • Brian Fluet is not online. Last active: 02-13-2020, 14:59 Brian Fluet
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    Re: AW: Re: Simultaneous access of different users to one mailbox by IMAP?

    Cool!

    Did you notice whether the MAILBOXM.LCK file was in place during the IMAP connections by Roundcube?

  •  01-08-2020, 10:07

    • PaulW is not online. Last active: 13 Feb 2020, 14:04 PaulW
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    Re: Simultaneous access of different users to one mailbox by IMAP?

    Brian Fluet:
    ... I suspect that a second IMAP connection attempt will be blocked when the Mercury lock is in place (MAILBOXM.LCK).

    As IMAP is a multi-user protocol this is most unlikely.  I believe the maim purpose of MAILBOXM.LCK is to prevent (or at least provide a strong warning against) opening a mailbox 'directly' when it's already being accessed by an IMAP client.

     

  •  01-08-2020, 10:21

    • Joerg is not online. Last active: 02-19-2020, 13:28 Joerg
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    AW: Re: AW: Re: Simultaneous access of different users to one mailbox by IMAP?

    Brian Fluet:
    Did you notice whether the MAILBOXM.LCK file was in place during the IMAP connections by Roundcube?

    Just checked, when accessing via Roundcube (means via Mercury I) no MAILBOXP.LCK or MAILBOXM.LCK will be set.

     

    edit:

    I have one user here who is always connecting via IMAP using Thunderbird. And in his mailbox directory I found a MAILBOXM.LCK. Tongue Tied It seems there are differences in accessing via IMAP.

     


    Mercury 4.81.187 @Windows Server 2016, with 16-100 user licence
    Pegasus 4.73.639, network installation
  •  01-08-2020, 13:45

    • Brian Fluet is not online. Last active: 02-13-2020, 14:59 Brian Fluet
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    Re: AW: Re: AW: Re: Simultaneous access of different users to one mailbox by IMAP?

    PaulW mentioned IMAP as a multi-user protocol which makes sense but got me to thinking about filtering.  I don't use IMAP so am not knowledgeable about filtering capabilities.  Could simultaneous filtering by multiple connected users be a problem or is filtering just local?

    I know very little about Roundcube but believe that it sits between Mercury and the user with user login to Roundcube and not directly to Mercury I.  If true. this would explain the lack of a lock file as compared to IMAP via Thunderbird or an iDevice directly to Mercury I.

     

  •  01-08-2020, 14:07

    • Joerg is not online. Last active: 02-19-2020, 13:28 Joerg
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    AW: Re: AW: Re: AW: Re: Simultaneous access of different users to one mailbox by IMAP?

    Brian Fluet:
    PaulW mentioned IMAP as a multi-user protocol which makes sense but got me to thinking about filtering.  I don't use IMAP so am not knowledgeable about filtering capabilities.  Could simultaneous filtering by multiple connected users be a problem or is filtering just local?

    I would take for granted that the filter rules are nevertheless working as expected, since all mailboxes will still be polled via POP3 Mercury D from our ISP mailboxes. And also the sending process will still be carried out via Mercury C and has to pass the Mercury Core Module.

    Brian Fluet:
    I know very little about Roundcube but believe that it sits between Mercury and the user with user login to Roundcube and not directly to Mercury I.  If true. this would explain the lack of a lock file as compared to IMAP via Thunderbird or an iDevice directly to Mercury I.

    But in the end Roundcube is also only an IMAP client. Roundcube is installed as a webserver in our company LAN (Linux server) providing an webmailer GUI where the user has only to navigate to an URL and needs the login credentials to its mailbox. Roundcube is directly interacting with your local (Pmail) mailbox, via Mercury I.

    I will made further tests during the next days to check whether any inconsistencies appear when different users simultaneously operating in one PMM file.


    Mercury 4.81.187 @Windows Server 2016, with 16-100 user licence
    Pegasus 4.73.639, network installation
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