[Exim] Excess Processes

We use a filtering service called Postini. They filter spam and virus emails
and then forward the cleaned email onto us. This problem creeps up
periodically the number of exim processes usually run about 15-20 in number,
but every so often the number of processes start building and never seem to
drop. We've upgraded to the latest version of exim cause it seemed to fix
the problem last time. Is there anything I can do to limit the number of
processes that will spawn? Right now its up to 140 processes and counting,
It stops responding to smtp and pop3 at anywhere from 50-100 processes. I
know its not my machine we're tried to completely different machines and it
does the same thing to both. We're running Slackware Linux on a dual AMD
2400MP machine with a 1 gig of ram. Any help or ideas would be greatly
appreciated.

The last time this happened was 5 or 6 months ago.