Outlook for Windows - Access Denied

Hello Tyler Cox,

I am sorry to hear that you are facing this persistent login error on your desktop app.

You have already performed some excellent troubleshooting steps, but the error code you are seeing suggests a corrupted authentication token that is "stuck" in the Windows security vault. In this specific case, simply reinstalling the application often isn't enough because the corrupted credentials remain stored in your Windows system. 

To resolve this, please follow these steps to clear the stuck data: 

Step 1: Nuke the Corrupted Windows Credentials 

1. Click the Windows Start button, type Credential Manager, and press Enter. 
2. Select Windows Credentials. 
3. Scroll down to the Generic Credentials section. 
4. Look for any entries that mention MicrosoftAccount, Outlook, Office, or Exchange. 
5. Click the drop-down arrow next to each one and select Remove. 
6. Note: This will not delete your emails; it simply forces Windows to forget the cached passwords so you can start fresh. 

Step 2: Deep App Reset 

1. Press the Windows Key + I to open your computer's Settings. 
2. Navigate to Apps > Installed apps (or Apps & features). 
3. Search for Outlook (new). 
4. Click the three dots ... next to it (or click the app name) and select Advanced options. 
5. Scroll down to the "Reset" section. 
6. Click Repair first. After the checkmark appears, click Reset and confirm the choice. 

Step 3: Final Sync 

1. Restart your computer one more time to ensure the Credential Manager and system memory are totally cleared. 
2. Open the New Outlook app. It should now behave like a brand-new installation. 
3. Add your account from scratch. The app will now pull a fresh, healthy authentication token from the server, which should bypass the error. 

I hope these steps help you get your desktop app back up and running smoothly. Please let us know if the issue persists or if you have any other questions! 

Quick note: I have edited the screenshot you provided to remove your personal information. Since this is a public community forum visible to everyone, please be careful not to include sensitive details (like your email address or phone number) in future posts to protect your privacy. 

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The error shown in the screenshot indicates that access to Outlook on this device is being blocked at the service side rather than by the local Outlook installation. Because Outlook works on smartphones and in a browser, the mailbox and credentials are valid, but the Outlook client on this device is denied.

For Outlook clients, when access is denied or blocked by policy or service configuration, this cannot be fixed from the device itself. The account or mailbox must be unblocked or re-enabled by the administrator or service support.

The appropriate next step is:

1. Contact the Microsoft 365/Exchange Online administrator for the account and provide the full error details (including correlation ID, timestamp, and code from the error dialog).
2. The administrator should open a support case in the Microsoft 365 Admin portal so Exchange Online support can review the logs and adjust the service configuration for the mailbox if needed.

While this is being investigated, Outlook on the web and Outlook mobile apps can be used as a workaround to access email.

References:

• Access Denied: Login Error
• Error when opening classic Outlook: "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed."