What you’re seeing
- The printer or application reports '5.7.57 Client not authenticated to send mail' when emailing through Microsoft 365.
- Scan-to-email stopped working right after someone changed the mailbox password used by the device.
- Alerts from a backup system, UPS or accounting package stopped arriving with no obvious error on screen.
- The device's settings appear correct, but every test message fails.
Common causes
Every environment is different, but these are the causes our engineers find most often:
- The device is connecting to the Microsoft 365 submission endpoint without providing a username and password.
- The password stored on the device is outdated after the mailbox password was changed or expired.
- Multi-factor authentication or security defaults now block the legacy sign-in the device relies on.
- The mailbox used for sending is unlicensed, disabled, or has had authenticated SMTP turned off.
- The device does not support the TLS version Microsoft 365 requires, so the secure sign-in never completes.
Why it matters
Devices that send through Microsoft 365 are often doing quietly important work: delivering scanned documents, invoice runs, system alerts and backup reports. When they fail, nobody gets warned that backups are failing or that payment reminders were not sent. The tempting shortcut of turning off security settings tenant-wide to make one printer work weakens protection for every account in the company.
How AskTechGurus fixes it
Skip the trial and error. A certified engineer works on your actual system, finds the root cause, and fixes it properly.
Tell us what’s happening
Submit a ticket in about two minutes. Paste the error, describe what changed, and pick your tier. No charge to submit.
A certified engineer diagnoses it
A vetted, US-based systems engineer claims your ticket, usually within minutes during business hours, and investigates over a secure remote session you can watch and end at any time.
Fixed and verified with you
The engineer resolves the root cause and confirms with you that it’s working. You don’t just get a workaround, and you get a plain-English summary of what was wrong.
Pay only when it’s resolved
Fixed price from $99, invoiced only after you approve the fix. If it isn’t resolved, you don’t pay.
Frequently asked questions
Why did this break when nobody touched the printer?
The printer relies on an account in Microsoft 365. A password change, a new security policy or a Microsoft change to sign-in rules can all break it without anyone touching the device.
Is there a way to send from devices that doesn't depend on a user's password?
Yes, there are several sending methods suited to devices and applications. Our engineer will explain which one fits your equipment and security setup before making a change.