Thank you very much for the information.  I will try out Cyris IMAP and 
SEIVE.
I posted this list because that's where the documentation to the IMAP 
utilities said to post.  I am very grateful for your help.
With kind regards,
Peter, hierodeacon
Rob MacGregor wrote:
It depends on how it's designed to work.  If it can be used as an 
MDA(Mail Delivery Agent) then you could probably use the mda option.  
See the man page for details.
<---SNIP--->
Any help/insights will be greatly appreciated.
As this list is all about fetchmail you'll probably have little success 
here.
I've recently set up CYRUS IMAP which comes with SEIVE, a filtering 
language.  Setting it up wasn't particularly hard (and there is a 
support list for it with lots of experienced people) and SEIVE should do 
what you're after.  I haven't however used SEIVE (yet) so I can't help 
with that.