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Dovecot compression

Discussion in 'E-mail Discussion' started by codepoet, Jul 25, 2017.

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  1. codepoet

    codepoet Member

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    Hello, since v66 of whm, we now have Dovecot compression.

    I read up on it, and understand by activating it, it will compress future emails from either mdbox or maildir accounts.

    Does this option affect reliability in any way ? as in data corruption or unable to read the compressed emails (using webmail or a client like outlook per example)?

    Thank you
     
    #1 codepoet, Jul 25, 2017
  2. cPanelMichael

    cPanelMichael Forums Analyst
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    Hello,

    I've not seen reports of any compatibility problems with email clients, or with data corruption, with the use of email compression. However, keep in mind cPanel 66 is only released to the Current build tier at this time. You may want to wait until cPanel 66 is in the "Release" or "Stable" tiers before using the feature if you are concerned about potential issues on a production system.

    Thank you.
     
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    #2 cPanelMichael, Jul 25, 2017
  3. codepoet

    codepoet Member

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    Hello @cPanelMichael

    Thanks a lot for the swift response. Indeed I forgot it was on Current build. But still thank you for answering.
     
    #3 codepoet, Jul 26, 2017
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  4. kernow

    kernow Well-Known Member

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    The default comression level is 6 but how high can you set it to? 10? 99?
     
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    #4 kernow, Aug 22, 2017
  5. cPanelMichael

    cPanelMichael Forums Analyst
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    Here are the requirements for this value:
    • “Compression Level” must be an integer.
    • “Compression Level” cannot be less than 1.
    • “Compression Level” cannot be greater than 9.
    Thank you.
     
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    #5 cPanelMichael, Aug 22, 2017
  6. kernow

    kernow Well-Known Member

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    Thanks for the info cPanelMichael.
    Wow this compression tool has saved GBs of space!! To compress already saved messages do the following:
    1) enable compression
    2) In WHM>>email>>>Mailbox conversion, change users mailbox format ( example maildir to mdbox ) and then change back again.
    Using the above method, on level 6 compression a users mail directory inbox of 5.5 GB mail box dropped to 3.5GB :)
     
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    #6 kernow, Aug 22, 2017
    Last edited: Aug 22, 2017
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  7. mtindor

    mtindor Well-Known Member

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    Changing the users' mailbox format back and forth does not compress existing email that was uncompressed before the running the script. Must have been some other reason for you suddenly freeing up 2 GB.

    I did the same thing as outlined by you, and it did not compress existing mail. cPanel then had me open a ticket, which I did. they confirmed that existing email doesn't get compressed using the CLI conversion commands or WHM --> email --> Mailbox Conversion. And they explained why, basically stating that the conversion scripts do not pass any of the existing messages through Dovecot as part of the conversion process and that it is within Dovecot where that compression happens. Makes sense to me.

    I'm glad you saw such a significant descrease in usage, but hopefully you didn't realize that decrease in usage at the expense of missing messages post-conversion.

    Mike
     
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    #7 mtindor, Mar 2, 2018
  8. kernow

    kernow Well-Known Member

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    #8 kernow, Mar 4, 2018
  9. mtindor

    mtindor Well-Known Member

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    Actually, it appears to compress all of the mail if I switch from mdbox back to maildir. But then, if I switch from maildir back to mdbox after that it appears that all of the m.* files except for the most recent ones (when I enabled compression in Dovecot) are uncompressed. Odd. I have converted one account's mailboxes back and forth half a dozen times. Every time I convert it back to maildir, every message in all mailboxes is a compressed file. Every time I convert it back to mdbox, only the m.* files that contain messages that arrived after I switched on compression are compressed.

    Mike
     
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    #9 mtindor, Mar 10, 2018
  10. cPanelMichael

    cPanelMichael Forums Analyst
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    Hello @mtindor,

    Keep in mind that the mailbox conversion workaround to compress existing emails is not supported or tested. It's just behavior that was noted in some cases and thus offered as a potential workaround. The best way to see this work is to have a feature implemented for the ability to compress existing emails. I see you have added a comment to the following feature request:

    Ability to compress existing email

    Thank you for taking the time to do that. It's the best approach to see support for this added to the product. I've also added my vote to this feature request.
     
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    #10 cPanelMichael, Mar 12, 2018
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