SMTP 550 5.7.26. — Unauthenti(92) email
What does this error mean?
The message is rejected because the authentication of the sender domain is insufficient according to the policy of the recipient.
Probable causes
Verification and resolution
- Check SPF
- check DKIM
- control DMARC alignment
Precaution: Do not modify DMARC without analyzing the path of sending.
Quick diagnostic.
To diagnose SMTP code 550 5.7.26 in the Email domain, start with the following check: Check SPF. Then check the result against this probable cause: SPF. Save the context and time of appearance to compare behavior before and after correction. Priority level indicated: High.