Observation on secondary MX

[Kevin Peuhkurinen]

About a month ago, there was a discussion on the list about how spammers 
specifically target secondary MX records.   After reading I verified 
that indeed 99% of the mail that flowed through my store-and-forward 
secondary mail server was spam.   So, I removed the second MX record 
from my DNS zone, but did not actually decommission the server itself.

The interesting thing is that now, about a month later, I'm still seeing 
spam going to that server!   I wonder if the spammers have cached the 
old MX entry or if they have some database of mail server addresses and 
what domains they will accept email for.