A mailer daemon, also known as a mail delivery agent or MDA, is a software program that manages the delivery of electronic mail messages. It acts as a middleman between the sender and recipient, ensuring that the message is successfully delivered to the intended recipient’s mailbox. The mailer daemon is responsible for handling any errors or issues that may arise during the delivery process, such as undeliverable addresses or full mailboxes. It plays a crucial role in the smooth functioning of email communication, ensuring that messages reach their intended destination in a timely and efficient manner.