Postfix is a popular open-source Mail Transfer Agent (MTA) that can be used to route and deliver email on a Linux system. If you manage a cloud server with applications that need to send email notifications, running a local send-only SMTP (Simple Mail Transfer Protocol) server is a good alternative to using a third-party email service or running a full-blown SMTP server. In this tutorial, you will install and configure Postfix to send emails by local applications only. Choose your operating system to get started.