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Subject: Postfix and Exchange Sharing a Domain?
From: Darron Froese (darronfroese.org)
Date: Tue Sep 19 2000 - 21:21:24 CDT

Background Info:

Head Office: Exchange Server on an NT Cluster (40 local users)
Satellite Office: Postfix on Linux (20 local users)

Neither office wants to be dependant upon the other for email service. The
head office Exchange server is *very* flaky and has stopped receiving email
on numerous occasions but the head office is still "the-head-office". The
satellite office's Postfix server works like a charm/dream/workhorse.

Here's the problem:

We would like to be able to receive email for "darrondomain.com" while they
also receive email for "userdomain.com" without:

Having a forward from their server to ours for each user (they can't be
trusted to configure it properly or keep it working)

OR

Us having to use luser_relay (because they probably won't allow the
satellite office to be the primary MX record as they're the "head office").
AND I wouldn't want them to get all the bounces (like luser_relay does). I
would just want them to get bounces for "userdomain.com" and not
"userotherdomain.com".

["usercity.domain.com" addresses are not an option either.]

I know that home does this (has multiple servers for the same domain name)
by forwarding all email to some incoming SMTP servers who then do some sort
of lookup (probably LDAP based - I'm not sure how they've done it) as to
where to actually deliver the message.

Is there *any* other way to accomplish this? Especially knowing that the
Exchange server is the primary MX record and that probably won't change. I
know that there would be problems (if it was able to even work) if two users
shared the same username somehow - two "bobdomain.com" users would
sporadically get each other's email.

This isn't a problem for us on our lan as I can canonically remap any email
for our local users (that would normally go to the head office server) to a
new local email server BUT it doesn't work with email from the internet that
doesn't pass directly through our email server. That's the most important
email to get. ;-)

I don't think it's possible but if I don't exhaust all my options looking I
won't be able to sleep properly - I need to know that I've done everything
that I possibly can to make this work - before going to the hassle of
changing our email domain and adresses.

I know this sounds really screwed up but it's the last option before we get
a new domain name so we can do it all ourselves.

Thanks. 

-- 
Darron
darronfroese.org