Again - noticing that I get a lot of spam atempts on the HIGHEST MX
record - I sert up a FAKE IP address for my highest MX.
I now have 3 MX records:
smtp1.ctyme.com - mail server
smtp2.ctyme.com - real backup server
smtp3.ctyme.com - fake backup server
The 3rd server - which is really just a different IP address on my main
server always returns DEFER creating a temporary error. Many spammers
never retry so the spam goes away. Is a very inexpensive spam deterrent
and have very low cost in computer resources.
defer log_message = Spammer Connected to FAKE highest MX record
condition = ${if
match{$interface_address}{209.237.228.13}{true}{false}}
delay = 3m
The delay gives me the illusion I'm punishing them.
There's no email losses because real email will eventually retry the
mail real server on the lowest MX record.