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5.5.1 Invalid command

The server did not accept a command in the conversation.

5.5.1 Invalid command

Permanent: retrying will not help

The server did not accept a command in the conversation.

Usual causes
  • A misbehaving mail script or client.
  • Trying to send before logging in, on a server that requires it.
What to do
  • Use a mail library or an email API.
  • Log in first, on the port your provider documents.

Usually the fault of: sender.

Common questions.

What does 5.5.1 mean?

The server did not accept a command in the conversation.

Will retrying fix 5.5.1?

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 5.5.1?

Use a mail library or an email API. Log in first, on the port your provider documents.

Other codes: 5.1.1 · 5.1.2 · 5.1.3 · 5.1.6 · 5.2.1 · 5.2.2 · 5.2.3 · 5.3.4 · Decode a whole bounce message

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