I've set up two Canon MFC printers to use SMTP relay with my Office 365 account, but they suddenly stopped scanning to email as of Monday. Nothing has changed on the firewall, Microsoft connector, or the printer settings – the public IP is still static and correct. However, I keep getting an error code #806 that says the username or password for sending to the email server might be incorrect. The email is linked to a shared inbox, which doesn't have a username/password set up. I'm starting to think this might be an issue on Microsoft's side. When I run the SMTP Test from the printer's GUI, it connects to the server just fine, but I'm at a loss about what else to check.
4 Answers
This seems to be a common problem with Exchange Online. Honestly, have you thought about using SMTP2Go or a similar service for your printer mail relays? It'll save you the headache of dealing with Microsoft’s quirks in the future.
We switched to SMTP2GO for our copiers after getting frustrated with Microsoft’s setup. It works seamlessly and keeps tabs on usage.
The crux of the issue is that shared mailboxes typically don’t have passwords and can't be directly authenticated with SMTP AUTH. Microsoft has been tightening security recently, so this might have caused your problems. It’s best to create a dedicated user account in Microsoft 365 for this purpose, as it will have a password and can be used for SMTP AUTH.
Just a heads up, after April 2026, they'll no longer support SMTP auth, so this might be a temporary fix.
I've seen this issue before and it's usually related to spoof settings. Check your mail protection service (like Defender or Proofpoint) to allow spoofing for the shared mailbox you're using.
I’m using Defender and added the address to the tenant allow/block list. Do you know if there's anything else I need to do?
Consider setting up a connector for your public IP and adding it to your SPF record. You can send directly using your exchange's MX record without needing authentication. Many overlook using the MX as the SMTP server instead of the typical smtp.office.com, which can save you from the auth hassle.
Absolutely! Just use Office 365 for personal emails and let third-party services manage direct relays.