Fix Microsoft SMTP Authentication Error

Quick Solution

If you’re encountering the error:

535 5.7.139 Authentication unsuccessful, SmtpClientAuthentication is disabled for the Tenant.

The easiest way to resolve this is by enabling SMTP authentication for your Microsoft 365 account.

Step 1: Enable SMTP Authentication in Microsoft 365

1. Go to the Microsoft 365 Admin Center.
2. Navigate to Users > Active Users.
3. Select the user account you’re using for SMTP authentication.
4. Under Mail > Manage email apps, ensure Authenticated SMTP is checked.
5. Click Save Changes.

Step 2: Use an App Password (if MFA is Enabled)

If Multi-Factor Authentication (MFA) is enabled for your account:

1. Sign in to Microsoft Security.
2. Go to Security Info > Add sign-in method.
3. Select App password and follow the instructions.
4. Use this app password instead of your regular password in Shipi.