SendMail is a simple program that can send e-mails via SMTP protocol.
Email Notifier For Windows
Local, web-based mail server application. Slurp mails into oblivion!
Client daemon to move mail from POP and IMAP to your local computer
Fast Bayesian spam filter along lines suggested by Paul Graham
Open source email service with a strong focus on security and privacy
Zentyal is a Linux Small Business Server
Take back control of your email with this mail server in a box
Command line management for Google G Suite
Liberté Linux: Mission-critical stealth communication
The cult-favourite eMail client formerly known as Qualcomm Eudora
Simple, web-based address & phone book
Catches mail and serves it through a dream