Manitou-Mail is a multi-component E-Mail application that includes:

Its architecture differs from traditional mailers in that the user interface is solely connected to the database, rather than IMAP/POP3 and SMTP servers. A server-side daemon program, manitou-mdx, is responsible for routing messages between the database and the mail subsystem, as well as filtering, indexing and custom-processing the stream of messages in background.

This is the documentation for the User Interface.