5.7.133 Microsoft bounce: group rejects outside mail
What 5.7.133 means
The recipient is a distribution group set up to reject mail from outside its organisation, so your message was refused.
Message text
Sender not authenticated for group
Common causes of 5.7.133
- Group is configured to accept only internal senders
How to fix 5.7.133
- Ask the group owner or the recipient organisation's administrator to allow external senders.
- Send to an individual mailbox in the organisation instead, if that suits the message.
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How to read 5.7.133
The second part, 5.7.133, is an enhanced status code (RFC 3463 §2) written class.subject.detail. Class 5 is a Permanent failure (5xx): the command was rejected and the sender should not repeat it unchanged (RFC 5321 §4.2.1; RFC 3463 §2).. Subject 7 is security or policy: authentication, authorization or policy refused the message. The detail number refines the subject, and providers may define details of their own, which is why one code can read differently at Gmail, Microsoft and Yahoo.
Do not keep resending the same message: a permanent failure repeats until the cause is fixed. Correct the cause, then send a new message.
Official source: learn.microsoft.com. Last verified 2026-10-20.
Related guides
- How to create an SPF record (syntax and examples)
- How DKIM works and how to publish a DKIM record
- How to set up a DMARC record, from p=none to p=reject
Related codes
- 5.7.0 SMTP: security status
- 5.7.1 SMTP: delivery not authorized
- 5.7.23 SMTP: SPF validation failed
- 5.7.25 SMTP: reverse DNS failed
- 5.7.26 SMTP: authentication failed
- 5.7.27 SMTP: sender has null MX
FAQ
What does 5.7.133 mean?
The recipient is a distribution group set up to reject mail from outside its organisation, so your message was refused. This is a permanent failure.
How do I fix 5.7.133?
Ask the group owner or the recipient organisation's administrator to allow external senders. Send to an individual mailbox in the organisation instead, if that suits the message.
Is 5.7.133 permanent, and should I retry?
5.7.133 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.