There are so many bounce codes used by the various ISPs and receivers that it's hard to keep them all straight. Now there is a great resource for most of the known bounce codes to help simplify your tracking and processing.
Thanks primarily to Chris Wheeler of Bronto Software, Jack Sinclair or Return Path and Josh Baer of OtherInbox, the eec’s Deliverability Roundtable has put together a repository of common and available bounce strings senders might see from current ISPs (email receivers).
The forum is setup on Get Satisfaction as a dynamic and interactive site that allows users to request information and update bounce strings as they change. The ISP serving the bounce, the bounce string text and next steps for a sender are written out by bounce code here.
For more information, visit the eec blog.