smtp load balance solutions

[Mike Dickerson]

I'm looking for an smtp load balancing solution (something
software based & open source is key ;) ).

I've seen http://www.freebsd.org.hk/html/sgcluster/
and wondered what folks had to say (pro or con). Anyone
using this?

Any other options? I'd be interested in hearing about non-
freebsd ones also (off this list would be best to reduce
the noise), but would prefer to stick w/ freebsd solutions.

The "ideal" (that I get from my boss) would allow "pass
through" if not being balanced (therefore a non-nat or
direct relation of external/internal ips). I haven't seen
anything that offers this (or have not dug sufficiently
through docs).

suggestions??


thx,

mike