Write email in Markdown and render them before sending
Zentyal is a Linux Small Business Server
Testable, composable, and adapter based Elixir email library
qpsmtpd is a flexible smtpd daemon written in Perl
Fast and robust e-mail parsing library for Rust
mailbox synchronizer
Robust open source POP3 client and MIME parser written in C#
SOGo Zero-Effort-Groupware
SaltOS, ERP, CRM, Business Management Suite, Josep Sanz Campderrós
Roundcube plugin to create client-side e-mail filtering.
software for email automation (newsletters, transaction mails, etc.)
Microsoft Exchange compatible server and client libraries