[exim] Workaround for port 25 blocking in complex roadwarrio…

I have a laptop running exim for mail-delivery. I have landed in a
situation where I need to use different SMTP relays to send mail, and
one of those is not run on port 25.

At home the ISP forbids outgoing port 25 connections, but provides an
SMTP-server which I must use as relay. At work the firewall prevents
outgoing connections to port 25 and *no* relay SMTP is provided ("we use
exchange for all mail", I am, of course working on that attitude -- but
things take time...).

I have figured out how to use fallback_hosts to attempt direct-delivery
first, and then try the relay. That however does not solve my problem at
work :(

To that end, I have an SMTP-server outside the company firewall, and I
have configured it to listen on ports 25 *and* 2525 and allowed relaying
from the company outgoing IP.

Now all I need is some way to use fallback_hosts with a different port
for one of the hosts. Unfortunatly it doesn't seem like that's possible.

I can't figure out how to use more than one transport for delivery,
which defeats declaring a "remote_smtp2525" transport, with "driver =
smtp; port=2525".

Any ideas?

BTW: Are there any retry parameters i should change to get things to
work for my road-warrior setup?

--
Helge