[exim] Probably simple ...

Folks,

I'm currently in the process of migrating away from qmail over to exim,
I'm almost there but I can't figure out how to set this up in the
config. I have the virtual users maildir location, however If there's a
.mailfilter file I want to use maildrop for delivery, if there isn't I
want to deliver straight to their mailbox.
Can someone give me a quick example of the recommended way to do this?

Steve.