535 5.7.139 — SMTP AUTH deactivated

535 5.7.139 — AUTH SMTP deactivated

What does this error mean?

Microsoft 365 refuses the SMTP authentication of the client because SMTP AUTH is disabled to the required level.

Probable causes

• SMTP AUTH disabled on the holder
• SMTP AUTH disabled on the box
• client using a d method, inherited authentication
• wrong configuration of sending

Verification and resolution

1. Check the holder’s SMTP AUTH configuration
2. Check the box concerned
3. Validate port, TLS and the login address
4. Privileg a modern method if the application allows

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