• 11 May 2025
• in Outlook, Office 365, Email
• 1 min read

Outlook logging into Office 365 Error

If you get an error 4usqa / 3399614475 when trying to log in to Office 365 from Outlook (desktop or mobile) all of a sudden as especially if it's multiple users, try the following:

1. Go to the Entra home page: https://entra.microsoft.com/
2. Sign in as a tenant admin
3. Search for Microsoft Information Protection API
4. Go to "Properties"
5. Select Yes for "Enabled for users to sign in?"

The solution was found on this Microsoft answers page.