exim config

[Nic Strong <nic@nscompservices.demon.co.uk>]

I have just installed exim on my box and it seems to be causing problems
when using fetchmail to get my mail from my ISP.

I configured exim using smarthost to deliver outgoing mail (suitable for
dialup option). But when using fetchmail from my ISP, I occationally
get mails from my ISP saying that I have had two processes trying to
access my mail at the same time. And with ppp established I get mail
delivered without even running fetchmail.
It wouldn't bother me but can't seem to find setting to control when
exim checks for new incoming mails.

Any help would be appreciated.

Cheers,
Nic