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).