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535 Authentication credentials invalid

The server refused your username and password, or your API key.

535 Authentication credentials invalid

Permanent: retrying will not help

The server refused your username and password, or your API key.

Usual causes
  • A typo, an old password, or a key that was revoked.
  • The provider needs an app password or API key instead of your normal password.
  • Two-step sign-in is on, and the account needs an app-specific password.
What to do
  • Check the username and password or key. Paste them again without extra spaces.
  • Create a new API key or app password and use that.

Usually the fault of: sender.

Common questions.

What does 535 mean?

The server refused your username and password, or your API key.

Will retrying fix 535?

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 535?

Check the username and password or key. Paste them again without extra spaces. Create a new API key or app password and use that.

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

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