530 5.7.1 Microsoft bounce: not authenticated
What 530 5.7.1 means
The receiving server does not accept anonymous mail from the Internet, so your sending server must authenticate first.
Message text
530 5.7.1 Client was not authenticated
Common causes of 530 5.7.1
- Sending server connects anonymously to a server that requires authentication
- Relay or smarthost misconfigured on the sending side
How to fix 530 5.7.1
- Use SMTP authentication or your provider's authenticated endpoint.
- Run MX lookup on the recipient domain to confirm you are delivering to the intended server.
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How to read 530 5.7.1
The first part, 530, is the SMTP reply code. Authentication required: the server wants the client to authenticate first (RFC 4954). Replies that start with 4 are temporary and replies that start with 5 are permanent (RFC 5321 §4.2.1).
The second part, 5.7.1, 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
- 5.7.1 SMTP: delivery not authorized
- 550 5.7.1 Gmail: likely unsolicited
- 550 5.7.1 Microsoft: delivery not authorized
- 550 5.7.1 Microsoft: unable to relay
- 5.7.0 SMTP: security status
- 5.7.23 SMTP: SPF validation failed
FAQ
What does 530 5.7.1 mean?
The receiving server does not accept anonymous mail from the Internet, so your sending server must authenticate first. This is a permanent failure.
How do I fix 530 5.7.1?
Use SMTP authentication or your provider's authenticated endpoint. Run MX lookup on the recipient domain to confirm you are delivering to the intended server.
Is 530 5.7.1 permanent, and should I retry?
530 5.7.1 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.