5.7.124 Microsoft bounce: not on allowed senders
What 5.7.124 means
The distribution group accepts mail only from listed senders, and your address is not on its allowed-senders list.
Message text
Sender not in allowed-senders list
Common causes of 5.7.124
- Sender is not on the group's allowed-senders list
- Group owner may also need to be on the list, depending on how the group is set up
How to fix 5.7.124
- Ask the group owner or administrator to add your address to the allowed-senders list.
- Send from the address that is already on the list if you have a second account.
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How to read 5.7.124
The second part, 5.7.124, 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 5.7.124 mean?
The distribution group accepts mail only from listed senders, and your address is not on its allowed-senders list. This is a permanent failure.
How do I fix 5.7.124?
Ask the group owner or administrator to add your address to the allowed-senders list. Send from the address that is already on the list if you have a second account.
Is 5.7.124 permanent, and should I retry?
5.7.124 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.