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SMTP codes

SMTP 251 User not local; will forward

The recipient is not on this server, but it will forward the message.

251
Class
2xx · Success
Retried?
Not needed
Defined in
RFC 5321

What to do

How it appears in a bounce

251 User not local; will forward

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

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