sendmail secondary server routing to alternate port

[Derrick Ryalls]

Greetings,

I recently had to rebuild my brother's all in one box to get a SATA
controller working.  It is now running 7.0 release and was previously
using courier and the mail system.  With this rebuild, I have switched
him over to sendmail and most things are working, but I discovered a
small issue with sendmail that I am having trouble working out.  As
well as being his own primary email server, he acts as secondary for a
couple of my domains, the tricky part is my ISP shut off port 25
access to me (no, I am not a spammer) so I use port 587 for handling
mail.  With courier, I was able to specify specific ports to
communicate with on a per domain basis.  For example, if I was
relaying for example.org on port 2345, I would specify
example.org:2345 and that is the port it would use to talk to
example.org.

Now that I have switched to sendmail, I don't see a way to set the
destination port on a per domain basis, only on an all or nothing
basis.  Am I missing some piece of the documentation or is this an
actual limitation of sendmail?