[exim] exim in queue mode but after some time queues are no …

exim 4.69 + few patches from cvs (buffer overflow fixes etc).

It's configured to be run in queue only mode + queues are run once per 15s.

Unfortunately after some time queue is no longer run, new mails are accepted
but not delivered.

Restarting exim fixes the problem for a while and after some time (few
minutes-few days) the problem appears again.

Any ideas on how to debug why queues are no longer run?

-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/