Postfix is ​​an extremely popular free and open source MTA (Mail Transfer Agent) software developed by Wietse Venema in 1997 and first released in December 1998. Postfix aims to provide a secure and reliable mail service that is resistant to Internet attacks and spam. To this end, Postfix has a number of security features, such as traffic restriction, server and client authentication, virus and spam filtering, and content filtering.