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Unable to read mail in Horde: Cannot allocate memory

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  • Unable to read mail in Horde with the following error:


    IMAP error reported by the server

  • The following message appears in /var/log/maillog while accessing mailbox:


    dovecot: service=imap, user=user@example.com, ip=[]. Fatal: master: service(imap): child 688159 returned error 83 (Out of memory (service imap { vsz_limit=256 MB }, you may need to increase it) - set CORE_OUTOFMEM=1 environment to get core dump)


  • The following error appears in /var/log/maillog during working in webmail interface:


    Error: mmap(size=0) failed with file /var/qmail/mailnames/example.com/user/Maildir/dovecot.index.cache: Cannot allocate memory

    and the size of the file /var/qmail/mailnames/example.com/user/Maildir/dovecot.index.cache is more than the default "vsz_limit" value:

    # ls -alh /var/qmail/mailnames/example.com/user/Maildir/dovecot.index.cache
    -rw------- 1 popuser popuser 500M Feb 27 11:21 /var/qmail/mailnames/example.com/user/Maildir/dovecot.index.cache
    # doveconf | grep default_vsz_limit
    default_vsz_limit = 256 M



The maximum limit for Dovecot process address space is reached.


  1. Connect to the server via SSH;

  2. Increase vsz_limit value in the dovecot configuration file by adding the following configuration:

    # touch /etc/dovecot/conf.d/99-vsz.conf
    # cat /etc/dovecot/conf.d/99-vsz.conf
    service imap { 
    vsz_limit = 512MB 

  3. Restart dovecot service:


    # service dovecot restart


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