Hi @mahekkalola ,
FluentSMTP uses Microsoft Graph for the Outlook/Azure connection, so an “Unauthorized” error after successful authorization usually indicates an expired/revoked token, expired client secret, sender mismatch, or a Microsoft 365 mailbox/security restriction.
Please try the following:
- Update FluentSMTP to the latest version.
- In Entra/Azure, confirm the client secret has not expired and that you copied the Secret Value, not the Secret ID.
- Confirm the app has delegated Mail.Send permission and admin consent has been granted if required by your tenant.
- Make sure the authenticated Microsoft account exactly matches the From Email in FluentSMTP. For a shared mailbox or alias, the account also needs Send As or Send on Behalf permission.
- Re-authenticate the connection in FluentSMTP and save a new access code.
If the issue continues, please send us the exact error message from FluentSMTP → Email Logs, along with your FluentSMTP version and whether the sender is a regular or shared mailbox. Please do not share your client secret, access token, or password. Also check the Microsoft Entra sign-in and Conditional Access logs at the time of the failed test, as tenant policies can revoke or block token renewal.
Thank you.
