[exim] heartbeat load balancing and exim

Just some ideas about using something like heartbeat to load balance 2
or more MTA servers. Say in the case you have 2 servers and wish to
combine them in a load balancing set up. This would require a 3rd server
to serve as a load balancer, either using heartbeat or a dedicated
machine like a cisco box.

If this is the case wouldn't implementing a load balancing setup
actually introduce more points of failure? You have halved the chance of
a failed MTA server causing downtime, but introduced the chance of the
load balancer failing, causing downtime of both MTA servers. You also
may have to deal with the added complexity of replicating the mailstore
on 2 (in this example) servers, and such a mechanism (using rsync, or
drbd) will have its own chance of failure.

Or is there a way to access a server directly, automatically, when a
load balancer fails? Maybe I am missing some obvious things.

Thank you,
Jeroen