install and setup IMAP and POP3 over SSL
Disable your css before visiting! Mail server HOWTO - Postfix and Dovecot with MySQL and TLS/SSL, Postgrey and DSPAM
receive and store email for your users from other mail servers on the internetlet your users retrieve the email through IMAP and POP3 - even using SSL-encrypted connectionsreceive and forward ("relay") email for your users using SMTP authenticationoffer a webmail interface to read emails in a web browserdetect most spam emails and filter them out or tag them