What is mailer daemon permanent error
A "permanent error" in the context of a mailer daemon, also known as a Mail Delivery System (MDS), is an error that prevents a message from being delivered to its intended recipient. This type of error is considered "permanent" because it is unlikely to be resolved on its own and requires manual intervention to resolve.
In the Simple Mail Transfer Protocol (SMTP), a mailer daemon is a program that acts as a mail server, responsible for receiving, processing, and forwarding email messages. When a mailer daemon encounters an error while attempting to deliver a message, it will typically return an error code and a descriptive message to the sender's email client.
A permanent error is typically indicated by a 5xx error code, which means that the message cannot be delivered to the recipient's email server. Some common examples of permanent errors include:
- 550: Requested action not taken (e.g., the recipient's email account does not exist)
- 552: Exceeded storage allocation (e.g., the recipient's email account is full)
- 553: Bad sequence of commands (e.g., the recipient's email server does not support a specific command)
- 554: Transaction failed (e.g., the recipient's email server is not available or is experiencing technical difficulties)
Permanent errors can occur due to a variety of reasons, including:
- Invalid or non-existent email addresses
- Email account suspension or deletion
- Server configuration issues
- Network connectivity problems
- Spam filtering or content restrictions
When a mailer daemon encounters a permanent error, it will typically bounce the message back to the sender with an error message indicating the reason for the failure. The sender's email client will then display the error message to the user, who can take action to resolve the issue, such as correcting the recipient's email address or contacting the recipient's email administrator.