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Microsoft 365 scan to email not working — SMTP AUTH disabled

If your MFP can no longer send through Office 365 and the log mentions SmtpClientAuthentication is disabled for the mailbox, this page is for you.

What changed

Microsoft disabled SMTP AUTH (basic authentication for sending mail) by default across Exchange Online tenants, as part of the same security push that removed basic auth for other protocols. Devices that had signed in happily for years began failing with 535 5.7.139 Authentication unsuccessful or an explicit “SmtpClientAuthentication is disabled” message.

Your options, honestly

Re-enable SMTP AUTH per mailbox. Possible with a PowerShell change, and it does fix the symptom — but you are re-opening basic authentication on a mailbox and storing that password in a device menu. Microsoft is steadily narrowing this path, so it is borrowed time.
Direct send / internal relay to your tenant. Works for internal recipients and needs no credential, but it won't deliver to external addresses, and it depends on your public IP's reputation.
An SMTP relay connector. The Microsoft-recommended route, and a sound one — but it means a static IP, a connector, certificate management and ongoing maintenance.
Modern auth on the printer. A handful of recent enterprise MFPs support OAuth 2.0 to Exchange. If yours does and you're happy configuring it, that's a good answer. Most devices in service today don't.

The straightforward fix

Give the printer an SMTP endpoint designed for it. Scanhive issues each device a dedicated short credential, speaks the SMTP dialects that MFP firmware actually implements, and delivers the scan onward from a verified domain with SPF and DKIM aligned — so Exchange Online accepts it like any other legitimate mail. No mailbox password on the device, no tenant-wide basic-auth exception, nothing to maintain.

What the settings look like

SMTP server	`smtp.scanhive.net`
Port	587 (or 25 on older devices)
Encryption	STARTTLS if offered — plain works for older firmware
Authentication	SMTP AUTH (LOGIN or PLAIN)
Verify server certificate	Off — see the note below
Username	from your dashboard, e.g. `prn_ab12cd34`
Password	shown once when you add the printer (rotate any time)

Brand-specific walkthroughs: Brother, Canon, HP, Xerox, Ricoh, Kyocera.

Don't have a Scanhive account yet? Create one free — adding a printer takes about a minute and gives you the username and password for the steps above.