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503 Bad sequence of commands

The commands arrived in the wrong order, such as the message body before the recipients, or a login after the message started.

503 Bad sequence of commands

Permanent: retrying will not help

The commands arrived in the wrong order, such as the message body before the recipients, or a login after the message started.

Usual causes
  • A script or mail client that skips or repeats SMTP steps.
  • A server that requires authentication before it accepts mail, and you did not authenticate.
What to do
  • Use a mail library that follows the protocol for you.
  • If you are sending through a provider, log in (authenticate) before sending, using the port and security setting they give you.

Usually the fault of: sender.

Common questions.

What does 503 mean?

The commands arrived in the wrong order, such as the message body before the recipients, or a login after the message started.

Will retrying fix 503?

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 503?

Use a mail library that follows the protocol for you. If you are sending through a provider, log in (authenticate) before sending, using the port and security setting they give you.

Other codes: 250 · 421 · 450 · 451 · 452 · 500 · 501 · 530 · Decode a whole bounce message

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