Hello,
| That is a big possibility, but how do I control my server
| from "using it too much"?
| Especially when you have several servers, for example.
what about using some filters _before_ checking dnsbls?
That can safe a lot of queries to the dnsbl.
i.e. doing greylisting first and after the mail comes back, do some
checks against dnsbls and other filters like spamassasin .. imho, the
advantage is big because the average 15 minutes greylisting can be
important -> the sender ip might be blacklisted on the dnsrbl within
that time ...