With email, you want simple, turnkey, and ideally self service.

Free::

http://modoboa.org/en/

http://www.iredmail.org/ ... also has paid version

Paid::

http://www.afterlogic.com/mailsuite/linux-email-server

https://www.atmail.com/

With each of the options above, you get the complete stack.

::Email server (IMAP + SMTP + POP3)

::Spam protection etc

::Web Client.

And for each of them, you also get a decent web admin panel out of the box.

Trust me, you really don't want to be spending the next week putting the individual components together and getting them to play nice yourself.