Problem: Any email that was sent to our mail server was being rejected by what looked like our spam filter. Getting a “550 Open Relay Database – see http://ordb.org” error. Made sure our spam filter was up to date, installed the update and rebooted. Still got the error.
Solution: Looked in the Spam settings and saw that Ordb.org was still listed in the RLB list. Removed it from the list and email was passing fine again. Read up on ordb.org and saw that it has been out of service for about a year and half. Don’t know why it all of a sudden gave false positives on all our email. At least it’s fixed now.