RE: SA gateway

[Michael Scheidell]

Firewall mail.example.com and don't let it accept any email from anyone but 
spamfilter.example.com
 
spambot might take several years to discover this.
 
In fact, set up mail.example.com as a secondary MX (and still keep it 
firewalled) 
why:
 
Reason #1, Disaster recovery, fail over
if spamfilters goes south, just adjust firewall.
 
#2, spammers are thinking that your secondary mx doesn't have a spam filter on 
it an go there first.
(you will cut out 50% of your spam just doing that)