Dovecot is an IMAP and POP3 server that interfaces with most MTA's like Sendmail Mail Server, QMail Mail Server and Postfix Mail Server.
Dovecot IMAP/POP3 Server main screen
Networking and Protocols
Dovecot Networking and Protocols
User and Login Options
Dovecot User and Login Options
User authentication can be arranged in various ways
Dovecot - Mail Files
To be able to use dovecot it has to know where the mail directories are, so you may have to suggest their location.
Dovecot SSL Configuration
Dovecot module configuration