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Error code wiki · 3 codes

Proofpoint SMTP error codes

Proofpoint sells email security to businesses and filters their incoming mail, scoring each sending IP with its own reputation system, Proofpoint Dynamic Reputation.

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Permanent failures (5xx)

2 codes

The receiving server refused the message for good. Your server will not try again, and the message comes back to you as a bounce.

  1. 550 5.7.1Sending IP blocked by Proofpoint Dynamic Reputation.Proofpoint’s IP reputation system has your sending IP on its block list because it has seen spam or viruses from it, so Proofpoint customers refuse your mail.Permanent
  2. 554Blocked by Proofpoint for spam or malicious activity.Proofpoint has blocked your sending IP or domain because of spam it received or malicious activity it detected, and the reply links to its postmaster page.Permanent

Temporary failures (4xx)

1 code

The receiving server cannot take the message now. Your server keeps it and retries, and only bounces it if the retries run out.

  1. 421Throttled by Proofpoint for unusual sending.Proofpoint is slowing down mail from your IP because its sending pattern looks unusual or unexpected. Your server should retry, and the delay often clears on its own.Temporary

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