hMailServer is a free and open-source software that will allow you to create your own mail server, and very quickly.
Indeed, this software offers all the necessary protocols (POP3, SMTP and IMAP).
hMailServer features :
- can be used with any webmail which supports SMTP and IMAP. (As SquirrelMail and RoundCube)
- integrated anti-spam protection
- possibility to use also a third-party anti-spam as SpamAssassin and ASSP
- ability to quickly configure an anti-virus analysis with ClamAV
- support of virtual domains
- available in several languages
- data can be stored on a MS SQL or MySQL server (choose during installation).