Despite the fact the Open Relay Database (ORDB) DNS Blacklist was shut down in December 2006 and operates no longer (DNS queries timed out since then), a large number of mail server administrators forgot to remove the ORDB definition from their filtering softwares (including ORF).
It seems the guys at ORDB finally had enough of the large number of queries to their servers and decided to return 127.0.0.2 responses to all queries instead of no answers (timeout). This means if you have ORDB enabled, it will blacklist all non-whitelisted mails… So it is strongly suggested to review your configuration to avoid such issues. (If you still have ORDB enabled in Configuration / Tests / DNS Blacklists, remove it immediately).
Quite aggressive measure from their part, but quite effective (and understandable if you ask me).
So it’s ORDB themselves… I was already thinking some spam tool included this list in their config (got some users here complaining about not being able to send mails out because rejected by ordb at the recipient side).
I have seen configs during my ORF support work which had ORDB enabled, but I never thought this many servers were affected…
BTW slashdot also published this:
http://tinyurl.com/2god7y