Tony pace wrote:
Thanks for all the input.
The diagram was "simplistic" - the real MSE is a couple layers away.
One thing that no one has mentioned is that it's vitally important that
the edge gateway (the postfix system) have a way of knowing what users
are valid. Otherwise you will end up with a lot of "invalid user"
bounces caused by dictionary spammers, which will either linger in your
queue or create backscatter spam.
At work, where I have Exim -> Exchange 5.5, I have Exim do an LDAP
lookup to determine whether a user is valid. There are other ways to do
it, though.
