RBLs

[elwood]

We experience some issues when we enable Real-Time Black Lists in the SPAM filtering.

When we add the presets for Spamhaus (SBL + XBL) and SpamCop together with a trigger count of 1 or 2 we do not receive any mail through the mail server.

All incoming mail is rejected with: Remote host said: 550 Recipient refused. Known spammer/exploit found, refer to http://www.spamhaus.org/query/bl?ip=206.190.48.115 (even though if you go to the URL, it says that this email is NOT SPAM).

When we only use one of the RBLs about 50% of the SPAM gets caught. I did notice while using SpamCop, we still receive some SPAM even know SpamCop has the IP tagged as SPAM. IE: http://www.spamcop.net/w3m?action=check ... 110.155.47

What am I doing wrong?

[rob]

RBL's depend on the ability to correctly look up domains, and if they don't exist, receive this answer correctly. However, sometimes on particular computers the lookups can always suceed for some unknown reason, which essentially means that RBL's can be unworkable. This fortuanatly is quite rare but it would seem that your system seems to be affected. I can only assume it is an error with your DNS servers which are returning postive answers to the RBL's DNS query. I would recommend you experiment with other RBL's, perhaps even adding them all and requiring a 3 or even 4 trigger count. I would also recommend enabling grey listing as this simple feature can have a huge impact on SPAM.