[Exim] Setting EXIM to deliver to alternate port

This is probably a FAQ, but I cannot search the mailing list archives
(ht://dig says there are plenty of refferences, but it won't show me any. I
only get the page index on the bottom. None of the pages have any message
links I can use).

I have a server that is listening for SMTP on an alternate port. I want to
setup my backup MX to forward to the alternate port instead of port 25. How
do I do that?

Thanks!
Dan Egli