Postfix is a free, open source mail transfer agent (MTA) originally written by Wietse Venema at IBM Research as a fast, secure, and easy-to-administer alternative to Sendmail. It runs on UNIX-like systems including Linux, BSD, and macOS, routing and delivering email over SMTP with extensive support for TLS, SASL, DKIM/SPF/DMARC integration… - View it on GitHub