Permanent failure — do not retry
SMTP 530 5.7.57
client not authenticated (Microsoft 365)
SMTP 530 5.7.57 is Microsoft 365 refusing mail from a device or app that connected to smtp.office365.com without signing in. Microsoft's text reads "Client was not authenticated to send anonymous mail during MAIL FROM." The fix is the device or app's SMTP settings.
How it appears
530 5.7.57 Client not authenticated to send mail. Error: 535 5.7.139 Authentication unsuccessful
530 5.7.57 Client was not authenticated to send anonymous mail during MAIL FROM
What causes it
- A printer, scanner or app is set to send through smtp.office365.com without credentials.
- Authentication is configured, but on the wrong port or without TLS.
- SMTP AUTH is disabled for the mailbox or for the whole tenant.
How to fix it
In order — try the first one first.
- Configure the device with the mailbox's credentials, port 587 and STARTTLS.
- Ask an admin to check that authenticated SMTP is allowed for the mailbox.
- For devices that cannot authenticate, use Microsoft's direct send or a connector instead.
Common questions
- What does SMTP 530 5.7.57 mean?
- SMTP 530 5.7.57 is Microsoft 365 refusing mail from a device or app that connected to smtp.office365.com without signing in. Microsoft's text reads "Client was not authenticated to send anonymous mail during MAIL FROM." The fix is the device or app's SMTP settings.
- Should I retry a 530 5.7.57 error?
- No. 530 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP 530 5.7.57?
- Configure the device with the mailbox's credentials, port 587 and STARTTLS.
Other 530 replies
Last reviewed 2026-09-11