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550 Requested action not taken: mailbox unavailable

The server refused the message and will not accept it if you retry. It is the most common bounce, and it covers many different reasons, so read the text and any dotted code after it.

550 Requested action not taken: mailbox unavailable

Permanent: retrying will not help

The server refused the message and will not accept it if you retry. It is the most common bounce, and it covers many different reasons, so read the text and any dotted code after it.

Usual causes
  • The address does not exist (look for 5.1.1).
  • The server rejected your message because of your domain’s setup or reputation (look for 5.7.1).
  • The recipient’s mailbox is disabled or blocks you.
What to do
  • Read the full message. The words and the dotted code after 550 say which of these it is.
  • Do not keep retrying. A permanent failure stays that way, and repeated attempts hurt your reputation.
  • Remove the address from your list if it does not exist.

Usually the fault of: either.

Common questions.

What does 550 mean?

The server refused the message and will not accept it if you retry. It is the most common bounce, and it covers many different reasons, so read the text and any dotted code after it.

Will retrying fix 550?

No. It is a permanent failure, so retrying the same message will not help, and repeated attempts can hurt your sending reputation. Fix the cause first.

How do I fix 550?

Read the full message. The words and the dotted code after 550 say which of these it is. Do not keep retrying. A permanent failure stays that way, and repeated attempts hurt your reputation. Remove the address from your list if it does not exist.

Other codes: 250 · 421 · 450 · 451 · 452 · 500 · 501 · 503 · Decode a whole bounce message

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