postfix question

[n j]

> You would probably get better assistance if you asked this question on
> the Postfix forum.

True. However, I did google through a lot of Postfix resources
(documentation, forums, mailing lists...) and didn't find what I was
looking for. I posted this question here hoping that someone already
ran into this problem, solved it somehow and was perhaps willing to
help me. I mean, people reading this list are system admins with
experience.

> Your machine isn't trying to establish a connection to: username at somedomain.com,
> it is trying to establish a connection to IP address x.y.z.a...

That is not relevant in my case. What I want to do is define two
different smtp services in master.cf (each bound to a different IP
address with smtp_bind_address option) and have Postfix use one or the
other based on incoming interface or sender's address/domain.

> You need 2 mailservers to do what you want.

That might be true with Postfix, although two instances on the same
machine would suffice - I'm looking for a solution that doesn't
include two instances. I know it can easily be done with Exim and I'm
actually testing on my test machine Exim installation right now.

Speaking of which, is FreeBSD with Exim a good combination for a
mailserver, what are your experiences?

Thanks,
-- 
Nino