Knowledge Base

Unable to read mail in Horde or Roundcube on Plesk for Linux: Cannot allocate memory due to vsz_limit

Symptoms

Plesk Obsidian running on a Linux-based operating system
Unable to read mail in the Horde or Roundcube webmail clients:

IMAP error reported by server

external ERROR
Could not load message from server
The following errors appear in /var/log/maillog:

dovecot: service=imap, [email protected], ip=[127.0.0.1]. 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)

Error: mmap(size=0) failed with file /var/qmail/mailnames/example.com/user/Maildir/dovecot.index.cache: Cannot allocate memory
Running the systemctl status dovecot command shows output that is similar to the following:
Apr 08 18:08:06 server dovecot[3588064]: master: Error: service(config): command startup failed, throttling for 60.000 secs
Apr 08 18:08:06 server dovecot[3588173]: config: Fatal: master: service(config): child 3868141 returned error 83 (Out of memory (service config { vsz_limit=256 MB }, you may need to increase it) - set CORE_OUTOFMEM=1 environment to get core dump)

Cause

The maximum limit for Dovecot process address space (vsz_limit) has been exceeded.

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

Resolution

Note: if you don't have root access to Plesk via SSH, contact your hosting provider regarding the issue

Log into the Plesk server via SSH
Open (or create) the file /etc/dovecot/conf.d/99-vsz.conf with your favorite command-line text editor and Increase vsz_limit value in the dovecot configuration by adjusting the contents as follows:
service imap {
vsz_limit = 1 G
}

default_vsz_limit = 1 G
Reload the Dovecot service in order to apply the changes:

# systemctl reload dovecot