Quite a common error with Dovecot running on Xen hypervisors, especially for clients who use cPanel on CentOS servers. Depending on the settings on your server, you might receive an error message like the following:
dovecot: Fatal: Time just moved backwards by 32779 seconds. This might cause a lot of problems, so I'll just kill myself now. http://wiki.dovecot.org/TimeMovedBackwards
It will not recover until you restart the IMAP service on your server. The issue is due to Dovecot not being very forgiving if your systems time moves backwards.
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Basic users: we suggest switching to Courier, which is more lenient for clock skew of this sort. It can be selected in WHM > Mailserver Selection when logged in to WHM.
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Advanced users: one workaround is to decouple the clock in the domU from the dom0:
In your dom0 and domU /etc/sysctl.conf add the line: xen.independent_wallclock=1. On the dom0, edit the configuration file of the domU (e.g. /etc/xen/foobar.cfg and add (or expand) the extra-line: extra="clocksource=jiffies"
These settings can be activated without rebooting the domU. After editing the configuration files, issue sysctl -p and echo "jiffies" > /sys/devices/system/clocksource/clocksource0/current_clocksource on the domU prompt.
Because the clock won't be relying on the dom0 clock anymore, you probably need to use ntp on the domU to synchronize it properly to the world.
