Knowledge Base FAQ Item #7500036

Q7500036: I want to use the Office365 legacy SMTP server smtp-legacy.office365.com. However, I receive an error "535: 5.7.139 Authentication unsuccessful, user is locked by your organization's security defaults policy".

You must disable the 'security defaults' in Microsoft Entra ID in order to use the legacy smtp-legacy.office365.com server.

To do so:

• Open Microsoft Entra Admin Center;
• In the search bar, search for 'Tenant Properties' and open it;
• Click on 'Manage security defaults' and select 'disabled'

You will now be able to use smtp-legacy.office365.com on port 587 using STARTTLS security on your password.