looking for email database

[Miles Fidelman <mfidelman@meetinghouse.net>]

Hi Folks,

A while back I came across a pretty neat piece of open source software 
providing a database for large scale mail storage, searching, and 
retrieval - with interfaces to all the standard MTAs and both POP and 
IMAP interfaces to the database.

For the life of me, I can't remember the name, and can't seem to find it 
via google.

Does this ring any bells for anyone?  Can somebody point me at it?

Thanks very much,

Miles