Decimail Server is a mail server supporting IMAP
and SMTP that uses a PostgreSQL database to store
messages. Mailboxes are defined using SQL queries,
allowing complex client-independent automatic
message filtering and categorisation. For example
you can partition your messages chronologically,
by correspondent, and by mailing list at the same
time, with each message appearing in several
mailboxes. You can also use PostgreSQL's text indexing
extension for fast keyword searching. Decimail also features anti-spam processing of outgoing messages.