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Email Compression

Discussion in 'E-mail Discussions' started by John Schmerold, Jul 31, 2017.

  1. John Schmerold

    John Schmerold Well-Known Member

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    If you have users that use POP3, do NOT enable email compression, convert from maildir to mdbox, then from mdbox to maildir. You will regret having done so.

    Every POP3 user is downloading thousands of emails in Outlook then calling me.

    It's going to be a long morning....
     
  2. cPanelMichael

    cPanelMichael Forums Analyst
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    Hello John,

    Could you open a support ticket using the link in my signature so we can review your system and verify if this is a flaw related to the mailbox conversion feature when compression is enabled?

    Thank you.
     
  3. John Schmerold

    John Schmerold Well-Known Member

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    Support Request ID is: 8755255
     
  4. John Schmerold

    John Schmerold Well-Known Member

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    Support says that this is normal behavior, I don't disagree, though I would have preferred that the conversion between mailbox types would have maintained the unique identifiers. So, long story short if you have users with large inboxes and using POP3 to check their mail, don't convert the mailboxes between mdbox and maildir.

    I used this command to get a list of POP3 users:
    grep -ris pop3-login /var/log/maillog

    Support looked at our server and said:
    "This is normal and intended behavior of accounts using POP.

    From this article specifically:

    Managing message downloads for POP3 accounts

    "Messages for a POP account are identified by unique identifiers (UIDs). An email client that leaves mail on the server uses the UIDL command to retrieve the UIDL map that associates each message that has been delivered to the mailbox to its UID. The client also gets the UIDL history for messages that have been downloaded or deleted for the Inbox on that client. Based on the UIDL history, the client can determine which messages are new and should be downloaded."

    What this means is that when you convert between mailbox types the UIDL identifier changes so the emails are marked as "unread".

    I would suggest switching to IMAP to prevent this. "
     
  5. cPanelMichael

    cPanelMichael Forums Analyst
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    Hello John,

    Thank you for sharing the outcome of the support ticket. Documentation case DOC-9301 is also open to ensure the Mailbox Conversion document is updated to reflect this information.

    Thank you.
     
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