5.7.23 Microsoft bounce: SPF violation

What 5.7.23 means

Exchange Online rejected the message because the SPF check for the sending domain failed.

Message text

The message was rejected because of Sender Policy Framework violation

Common causes of 5.7.23

• SPF record does not include the sending IP or service
• SPF record has syntax errors or too many DNS lookups

How to fix 5.7.23

1. Run SPF checker on the From and envelope domains.
2. Add the sending service's include or ip4 mechanism to the SPF record.

Check your domain

Check the SPF record of your sending domainRuns in your browser; nothing is uploaded.

Have the full bounce message? Paste it into the bounce code lookup and it will match the code and the provider for you. Open the bounce code lookup.

How to read 5.7.23

The second part, 5.7.23, 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

• SPF syntax errors: every checker message explained
• How to create an SPF record (syntax and examples)
• SPF “too many DNS lookups”: why it happens and how to fix it

Related codes

• 5.7.23 SMTP: SPF validation failed
• 5.7.0 SMTP: security status
• 5.7.1 SMTP: delivery not authorized
• 5.7.25 SMTP: reverse DNS failed
• 5.7.26 SMTP: authentication failed
• 5.7.27 SMTP: sender has null MX

FAQ

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