I switched over to Comodo’s DNS a few days back because our ISP’s DNS servers were having problems. Since then, our SpamAssassin installation has been reporting all kinds of false positives, mainly identifying many safe URL’s as being on one or more of the SURBL blocklists. A check on SURBL’s web site shows that these URL’s are not actually on their blocklists. I switched back to our ISP’s DNS servers (hoping that they had things back under control), and the SpamAssassin false positives disappeared and our email is back to normal.
This has scared me off of ever using Comodo’s DNS servers again unless I can figure out how to avoid this email problem in the future. Can anyone enlighten me as to what was going on? Why/how do Comodo’s DNS servers affect SpamAssassin’s SURBL queries and result in these false positives? And, is there a way around this?