[Exim] Exim Server crashes intermittently

Hello List,

About three weeks ago our mail server started to crash, after running
without problems for three years. It was an Exim 3.x installation on SuSe
Linux, so we thought it might have to do with missing updates, old software
versions or something of that kind.

We have reinstalled the server on new Hardware, the latest Linux version,
and the latest Exim and QPopper release, but still the server crashes every
36 hours. However, if I reboot the server every 24 hours nothing happens.

I can't find any hints in the log files, and I don't even know if it has to
do with exim or qpopper. Other programs aren't installed on this machine.
The server just crashes, all services go unavailable and no login is
possible from the console. After a hardware reboot it will run again for
about 36 hours.

Can anybody point me in some direction where to start debugging this
problem? Could it be a denial of service attack?

Thanks in advance
Beo Lutz