We have added the possibility for SpamDrain users to turn off the DNS blacklist filter which currently blocks messages sent from known spam servers. Why would you want to do that, you might wonder? (…or you just wonder What is DNS blacklisting ;-)).
Some users in spam intensive countries gets almost all their messages blocked because of their ISP has servers listed in the blacklists. They might also communicate with other users that have their mail servers blacklisted. These ISP:s do very little to be removed from the blacklists for some reasons, or they just don’t have the knowledge to stop the spammers from utilizing their servers. Such users obviously have no use of the blacklist filter and should disable it. The normal AI based SpamDrain filtering will do a much better job without the help of this filter.
To do that you Log on to the SpamDrain site and click Settings->Other. Uncheck the box “Block messages from servers listed in public black lists.” and SpamDrain will stop blocking messages only because it has been sent through a blacklisted server.
For some time, we have tested DNS blacklisting as a step after the normal SpamDrain filter. However we have not yet evaluated if the filtering gets better by doing so. What we hear from our users, the filtering works really good – even without the blacklisting we believe. So we might change this in the future.