DBMail is a Message Delivery Agent speaking IMAP, POP, ManageSieve and LMTP using industry standard PostgreSQL, MySQL and Oracle for secure scaleable storage.
What are the advantages?
IMAP is the industry standard for communicating with email clients.
PostgreSQL, MySQL and Oracle bring scaleability and continuous replication so your emails are stored safely.
DBMail can manage users, it can also connect with OpenLDAP or Active Directory for integrated user management.
Written in C, DBMail is efficient. Its component parts can be scaled out to as many servers as required.
Integrates with most Message Transfer Agents such as exim or postfix with either command line using dbmail-deliver or LMTP. Exim integration simplifies end user configuration by leveraging the same authentication sources, sql and ldap, for SMTP and IMAP login, as well as checking valid emails before accepting incoming mail.
Integrates with front end email web servers such as squirrelmail and roundcube.
DBMail is secure as it doesn't require access to any filesystem other than for its own configuration and log files. It's as secure as the database and directory server.