Office 365 scan-to-email not working

Updated: July 2026

Your copier or printer no longer emails scans, often with an error like 5.7.139 SmtpClientAuthentication is disabled or a rejected login. The most common cause in 2026: Microsoft is retiring basic authentication for SMTP, and the device cannot switch to modern authentication.

Why it breaks

A copier usually sends to smtp.office365.com with an address and a password. When Microsoft disables that basic authentication, the device is stuck. And many copiers (Canon, Konica, Xerox, Ricoh, HP) have no firmware that handles OAuth, or handle it poorly.

The fluctuat fix

You point the copier at your fluctuat endpoint with a dedicated credential, exactly like a classic SMTP server. fluctuat speaks modern authentication to Microsoft 365 on its behalf, and the scan goes out as the intended address, within your own tenant. No firmware to change, no OAuth to configure on the device. And the credential can be restricted to the copier's IP, so it is useless elsewhere if it leaks.

Frequently asked

Which devices? Any copier or printer that can point at an SMTP server with a credential and a port (587 or 465).

Do we have to change the scan addresses? No, you keep the usual sender address.

Create an account, first send in ~15 min

Free to start, no card. A Sovereign edition is available for sending that never transits through Dizzus.