Mail Replication

[Vampire D]

We are looking at building an environment with FreeBSD using HeartBeat as
well as Master-Master replication for mySQL so we can provide complete
fail-over for a apache/mysql/php project for short money.  But since I
cannot find a solution like DRBD (which looks absolutely perfect for us, but
I refuse to use Linux) on FreeBSD I am forced to use mySQL replication and
Master-Master appears the best way to avoid some of the problems typically
faced with replication.   But we still are left with replication mail stores
with postfix.

In short, is there any good reliable solution to have two boxes cluster mail
delivery so if the master fails, the secondary can keep going without any
loss of services?  With DRBD we could probably manage something with the
replicated block device, but using FreeBSD we are stuck with mySQL
Replication and no solution for mail.

Any advice / suggestions would be great.  We are trying to build a
completely automated fail over solution for two servers using Apache, mySQL,
PHP, and Postfix within a small monthly budget.

-- 
"Do the actors on Unsolved Mysteries ever get arrested because they look
just like the criminal they are playing?"

Christopher