LinuxQuestions.org - eXtremail and Blacklists

I've been using eXtremail as my mail server for several years now. Within the last eight months or so, spam has become a real problem, so I became interested in implementing DNS blacklist features on my mail server.

eXtremail has blacklist support for Realtime Blackhole Lists and Dial-up User Lists since version 1.5-3 (I believe). But, just be sure I got all the latest stability and security fixes and the latest features, I upgraded to version 1.5-9.

Here's my dillema: I have my eXtremail.conf file set up as follows:

Code:

BlacklistMapsRbl = Yes

BlacklistMapsDul = Yes

BlacklistServerMapsRbl = blackholes.mail-abuse.org

BlacklistServerMapsDul = duinv.aupads.org

So, technically, the blacklist features should be enabled. However, when checking the mail server's logs, I frequently find errors like this:

Code:

DNS - No answer header found on DNS response. Quitting.

...And I continue to find spam in my inbox as usual. I've tried using other blacklist servers, and all with the same effect. Any ideas as to what I could be doing wrong?

Thanks in advance.