If you’re encountering the dreaded Outlook Error Code CAA2000B when trying to sign in, you’re not alone. This issue is affecting many Microsoft 365 users across different organizations. Fortunately, there is a clear and effective fix available that gets things back up and running quickly.
🚫 What Is Outlook Error Code CAA2000B?
This error occurs when Outlook cannot authenticate your sign-in request due to a disabled backend application called the Microsoft Information Protection API. This API is critical for authentication flows, especially in enterprise environments using Azure Entra (formerly Azure AD).
In recent months, many Microsoft 365 tenants have found this app disabled in their Microsoft Entra settings, which breaks the Outlook sign-in process and triggers error CAA2000B.
✅ Quick Summary of the Fix
- Re-enable the Microsoft Information Protection API in Entra.
- Clear Microsoft Teams cache on affected machines.
Let’s walk through each of these steps.
🔧 Step 1: Re-enable Microsoft Information Protection API in Microsoft Entra
To do this, you need access to the Microsoft 365 Admin Center with either Global Admin or Application Admin permissions.
Instructions:
- Sign in to the Microsoft 365 Admin Center.
- In the left-hand sidebar, click on All Admin Centers.
- Select Microsoft Entra ID (formerly Azure Active Directory).
- From the Entra dashboard, click on Enterprise Applications.
- Clear any filters at the top so you can view the full list.
- In the search bar, type:
Microsoft Information Protection API - Click to open the application properties.
- Locate the setting “Enabled for users to sign in”.
- If it’s toggled off, switch it on.
- Click Save.
✅ This step re-enables Outlook’s ability to communicate with the Information Protection service, which is the root cause of error CAA2000B.
🤔 Why This Happens
This change often happens due to automatic configuration changes in Azure environments or organizational security adjustments that unintentionally disable the API. Once it’s off, Outlook can’t complete authentication for users.
🔍 Step 2: Clear Microsoft Teams Cache
After re-enabling the application in Entra, it’s important to clear the Teams cache on affected devices. The cache can hold outdated login data that blocks the fix from taking effect.
How to Clear Teams Cache (Windows):
- Open File Explorer.
- In the address bar, paste:
%appdata%\Microsoft\Teams
- Press **Enter**.
- Delete **everything inside the folder** (don’t delete the folder itself).
- Close File Explorer.
- Restart **Microsoft Teams** or reboot your PC.⚠️ Teams shares authentication sessions with other Microsoft 365 apps, including Outlook. That’s why this step is crucial.
🚀 Step 3: Relaunch Outlook
Now that the API is enabled and your cache is cleared:
1. Open Outlook again.
2. You should be able to **sign in without seeing error CAA2000B**.
If you still encounter issues:
– Double-check that the API is **enabled in Microsoft Entra**.
– Ensure the changes were saved properly.
– Make sure your admin account has sufficient permissions.
✉️ Final Tips
– Use Microsoft’s **diagnostic tools** to confirm Entra configuration.
– Keep your **Outlook and Teams apps updated**.
– **Communicate changes** with your IT team to prevent future errors.
