Bounce codes › Microsoft 365
530 5.7.57: Client was not authenticated to send anonymous mail during MAIL FROM
A printer, scanner, website or app tried to send email through Microsoft 365 (smtp.office365.com) without logging in properly. The message was never sent.
Fix your sending setup Sending is not set up correctly
The app or device sending through smtp.office365.com is not logged in correctly.
- Sent by: Microsoft 365 / Outlook
- Permanent (hard bounce). Sending the same message again fails again.
How Microsoft 365 words it (source):
Client was not authenticated to send anonymous mail during MAIL FROM
Why it happens
- Wrong username or password in the device or app.
- The mailbox has "Authenticated SMTP" switched off. It is off by default in newer organisations.
- The device does not use TLS on port 587.
- Multi-factor authentication is on for the mailbox and the device cannot do it.
What to do
- Set the device to server
smtp.office365.com, port 587, STARTTLS, with the full email address as the username. - Ask your Microsoft 365 administrator to enable Authenticated SMTP for that mailbox.
- Make the From address the same as the mailbox you log in with.
- For devices that cannot log in at all, Microsoft offers "direct send" and "SMTP relay" through a connector instead.
Don't confuse it with
This is not a bounce from a recipient. No address on your list caused it.
Questions
Does this mean the recipient rejected my email?
No. Your own mail provider refused to take the message from your device.
It worked for years. Why did it stop?
Usually a password change, or a change in the organisation's security settings that switched off basic sign-in for SMTP.
Got a different bounce?
Paste the whole message into the bounce code lookup. It reads the code and the words and tells you whose move it is.
Related codes
550 5.1.8Access denied, bad outbound sender (Microsoft 365)