Can't create PID PostMasterMailbox, because it's already running

[numerouno]

Happy new year to all.

I am seeing a lot of the follow error message: Can't create PID PostMasterMailbox, because it's already running! This occurred in OTRS 3.3.7 and also after upgrade to OTRS 4.0.2.

Google has not helped resolving this one, the process appears to be hanging. ps -ef | grep PostMasterMailbox.pl:

otrs 12889 12888 0 09:32 ? 00:00:00 /bin/sh -c $HOME/bin/otrs.PostMasterMailbox.pl >> /dev/null
otrs 12891 12889 0 09:32 ? 00:00:00 /usr/bin/perl /opt/otrs/bin/otrs.PostMasterMailbox.pl

I can kill the processes and delete process in MySQL DB, but this is a temporary fix.

Can anyone assist with a permanent solution to this intermittent issue?

[crythias]

It usually means it's fetching too fast or too often. Stop cron and kill all processes and do a force to clear it out. Start cron again.