Sendmail

Sendmail is a widely used [[Mail Transport Agent (MTA)]] in Unix-based systems. It's a powerful, open-source software application that's responsible for routing and delivering email messages from one host to another, using the [[Simple Mail Transfer Protocol]] (SMTP).

Sendmail transfers emails from the sending system to the recipient's mail server, handling decisions about routing based on various factors like domain names and network conditions. It is known for its highly configurable nature, allowing extensive control over how email is processed, routed, and delivered.

The configuration of Sendmail can be quite complex, often requiring in-depth knowledge of system administration and the Sendmail configuration language. It can handle a large volume of email traffic and is capable of dealing with complex mail-processing operations, making it suitable for large organizations.

Over the years, Sendmail has incorporated numerous security features to handle vulnerabilities and protect against threats like spamming and email relay abuse.

Sendmail was widely adopted in the early days of email and is still in use, especially in legacy systems. However, its complexity and the rise of alternative MTAs (like [[Postfix]] and [[Exim]]) have led to a decrease in its popularity. It's often used in large-scale and complex email environments due to its robustness and extensive configurability.