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Error code wiki · 11 codes

Barracuda SMTP error codes

Barracuda Networks makes email security gateways, as appliances and as a cloud service, that screen incoming mail for businesses using its own reputation list among other checks.

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Permanent failures (5xx)

8 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. 550SPF check failed.The recipient’s Barracuda gateway checked the SPF record of your sending domain, found your server not authorised, and rejected the message.Permanent
  2. 550Rejected as spoofed.The recipient’s Barracuda gateway decided your message pretends to come from a sender it does not really come from, and refused it.Permanent
  3. 550Sending IP blocked by the recipient.The recipient company’s Barracuda gateway refuses mail from your sending IP, usually because an administrator has added it to a block list on their side.Permanent
  4. 550Sender address blocked by the recipient.The recipient’s Barracuda gateway refuses your sender address or domain, usually because the company has blocked it.Permanent
  5. 554Sending IP or domain on a real-time blocklist.The recipient’s Barracuda gateway refused the connection because your sending IP or domain may be on a real-time blocklist (RBL) it checks.Permanent
  6. 554Blocked by Barracuda Reputation.Barracuda’s own IP reputation list scores your sending server as a spam source, so every Barracuda gateway checking it refuses your mail.Permanent
  7. 554Rejected as spam.The recipient’s Barracuda gateway scanned your message, judged its content to be spam and refused it.Permanent
  8. 554No reverse DNS for the sending IP.Your sending IP has no reverse DNS (PTR) record, and the recipient’s Barracuda gateway is set to refuse servers without one.Permanent

Temporary failures (4xx)

3 codes

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

  1. 420Deferred for suspect content.The Barracuda gateway found something suspect in your message and asked your server to try again later, holding it back while it decides.Temporary
  2. 421Too many messages in one session.Your server sent more messages over a single connection than the Barracuda gateway allows, so it closed the session. The remaining messages retry on new connections.Temporary
  3. 454Too many connections (rate control).Your server opened more connections to the Barracuda gateway than its rate control allows, so the gateway is turning it away for now.Temporary

Every code in the wikiPaste your own bounce

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