[Exim] changing smtp-port for certain hosts

Hello,


I have kind of a strange problem. Some of the hosts
I maintain are behind a firewall blocking port 25.
I would like to send them email directly using another
port than 25. I looked through the docs and it looks
like it can be done, but as an exim newby it is rather
complicated. So my question is:

Can I change the smtp-port to deliver mail to certain
hosts and how can this be done (an example that I
can modify and glue into my /etc/exim.conf)?

Thank you very much for any help you can give,

Fulko
--
Fulko van Westrenen
email: f.c.v.westrenen@???
TUE/IPO, center for user-system interaction