[Exim] Firewall and Mailserver

Yeh I was just wondering if someone had a quick answer for this...

Alright I had exim set up and everything was working great... then
company decides that they want a firewall in front... alright So I set
up a OpenBSD firewall in the front using ipf and ipnat ....
I redirect all the traffic from port 25 and 110 from the firewall to the
mailserver ... but now I can't get mail or send any out... is there
anything that I am missing here... what should I have done ... or what
should I do now???
my ipnat rules are using rdr (redirect) so I am assuming that it should
have worked... does exim use none standard ports or something that I am
not aware of.

Any help would be appreciated.