Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
Inbucket - Inbucket is an email testing application; it will accept messages for any email address and make...
mailcow - An open source mailserver suite.
Mail-in-a-box - Mail-in-a-Box provides webmail and an IMAP/SMTP server for use with mobile devices and desktop mail software and also includes contacts and calendar synchronization.
MailHog - MailHog is an email testing tool inspired by MailCatcher, but easier to install.
MailerQ - MailerQ is a high performance Mail Transfer Agent (MTA) designed for delivering large volume email messages at very high speeds.