[Exim] Outlook AUTH + TLS on a non-standard port

This may be too obscure for a sane person's interest. But by now I'm not
only frustrated but really curious as to why this doesn't work.

I have Exim 4.02 happily servicing Outlook 2000's "outbound messages" using
both SMTP AUTH and TLS on port 25. Motivated by a friend whose ISP appears
to be blocking port 25, I tried running the same Exim config on port 23 (we
don't use telnet anyway). Then I changed the value for Outlook's outgoing
mail server port. Simple enough, right? Now I suddenly get connection
failure errors in Outlook when I try to send out mail. Nothing ever hits
my linux box (or exim's logs). Outlook just prints its generic "Account:
foo, Server: outbound, Port: 23, SSL: Yes" message but with no specific
error. Well, I think it may say something like "Socket Error: 110110" (I
just made that number up).

Interestingly enough, Outlook --> Exim works on port 23 if I disable
outbound SSL/TLS. Could Outlook have something hard-coded to port 25 for
SSL even though they give you the option to change it? Does anyone have
experience with this? I've tried running Exim on 25 and port forwarding
something else to it. But the problem consistently appears to be on the
desktop side.

Confused,
-R

--
Rick Ennis