Dbmail is the name of a group of programs that enable the possibility of
storing and retrieving mail messages from a database (currently MySQL,
PostgreSQL or SQLite).

* Scalability.
  Dbmail is as scalable as the database system that is used for the mail
  storage. In theory millions of accounts can be managed using dbmail. One
  could, for example, run 4 different servers with the pop3 daemon each
  connecting to the same database (cluster) server.
* Manageability.
  Dbmail is based upon a database. Dbmail can be managed by changing settings
  in the database (f.e. using PHP/Perl/SQL), without needing shell access.
* Speed.
  Dbmail uses very efficient, database specific queries for retrieving mail
  information. This is much faster then parsing a filesystem.
* Security.
  Dbmail has got nothing to do with the filesystem or interaction with other
  programs in the Unix environment which need special permissions.  Dbmail is
  as secure as the database it's based upon.
* Flexibility.
  Changes on a Dbmail system (adding of users, changing passwords etc.) are
  effective immediately.

WWW: http://www.dbmail.org/