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SMTP codes

SMTP 455 Server unable to accommodate parameters

The server cannot accept the MAIL FROM or RCPT TO parameters right now. Temporary.

455
Class
4xx · Temporary failure
Retried?
Yes, the sending server retries
Defined in
RFC 5321

What to do

How it appears in a bounce

455 Server unable to accommodate parameters

Paste the full bounce into the decoder — it finds every code and recipient and says what to check.

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