Your #1 option is to just simply reject incoming mail for those
accounts, at the SMTP level, that way the sending mail server never even
gets to use up your bandwidth by transmitting the data of the message.
That means you either use the CHKUSER patch, which allows you to reject
mail for non-existing users, and delete those users... OR you could use
the badrcptto patch ... CHKUSER doesn't work if you've got a catch-all
account set to anything other than bounce...
But definately if bandwidth is your concert, you'll want to use one of
those methods.
Greylisting can also help by rejecting a lot of incoming mail
"temporarily". I use Bill Shupp's greylisting patch (www.shupp.org)
Rick
