SpamAssassin - Use this program to "Unspam" your mailbox(es).
Roundcube - Web-based IMAP email client
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
Mailpile - Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features.