Postfix is a popular open-source mail transfer agent (MTA) used to route and deliver email on Unix-like operating systems. It is designed to be fast, secure, and easy to configure, making it a preferred choice for many system administrators. Postfix handles the sending and receiving of emails, managing tasks like queuing messages and ensuring they reach their intended recipients. One of the key features of Postfix is its modular architecture, which allows for easy integration with other software and services. It supports various protocols, including SMTP (Simple Mail Transfer Protocol), and can work alongside other tools like Dovecot for email retrieval. This flexibility makes Postfix suitable for both small and large email systems.