Mailer Daemon

A Mailer Daemon is a computer program used by email servers to notify you when an email you sent couldn’t be delivered to the intended recipient. It acts like a digital postmaster, sending you a message that explains why your email returned to you, such as an invalid address or a full mailbox. These messages help you identify and correct delivery issues. Essentially, it’s a system-generated report indicating that your email did not reach its destination and providing reasons for the failure.