Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
Mailtrap - Email Delivery Platform that delivers just in time. Great for businesses and individuals.
mailcow - An open source mailserver suite.
FakeSMTP - FakeSMTP is a Free Fake SMTP Server with GUI for testing emails in applications easily.
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.
MailCatcher - MailCatcher runs a super simple SMTP server which catches any message sent to it to display in a...