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How to Fix Outlook Error 0x80070021 on Windows 11: Step-by-Step Solutions

Outlook error 0x80070021 is a common issue that can disrupt your email experience on Windows 11. This error usually occurs when Outlook is unable to access certain files or resources because they are being used by another program. Fixing this problem can help restore smooth email operations.

In this article, you will find simple, easy-to-follow solutions to resolve error 0x80070021 in Outlook. Each step is explained in detail to help even beginners understand the process.

By following these instructions carefully, you can quickly get Outlook back to normal without needing advanced technical knowledge. Let’s begin with some quick checks before diving into the fixes.

These steps will take you from the simplest solutions to more advanced ones, ensuring you don’t miss anything important.

Quick Note: Prerequisites and Initial Checks

Before starting the troubleshooting, make sure you have the following in place:

  • Close all other programs: Sometimes, other applications might be using Outlook files, causing the error.
  • Restart your computer: This helps clear temporary file locks or conflicts.
  • Check internet connection: A stable connection is necessary for Outlook to sync properly.
  • Update Windows and Outlook: Ensure both your operating system and Outlook app are updated to the latest versions.

Step 1: Close Conflicting Programs

The error 0x80070021 often happens because another program is using the same file Outlook needs. To fix this, you need to close those programs.

  1. Press Ctrl + Shift + Esc to open Task Manager.
  2. Look for any software that might be using Outlook files, such as other email clients, backup tools, or antivirus programs.
  3. Select the program and click End task.
  4. Try opening Outlook again to see if the error is resolved.

This step is important because file conflicts prevent Outlook from accessing necessary data, causing the error.

Step 2: Disable Add-ins in Outlook

Add-ins extend Outlook’s functionality but can sometimes cause conflicts that lead to errors.

  1. Open Outlook in safe mode by pressing Windows + R keys.
  2. Type outlook.exe /safe and press Enter.
  3. If Outlook opens without error, go to File > Options > Add-ins.
  4. At the bottom, select COM Add-ins and click Go.
  5. Uncheck all add-ins and click OK.
  6. Close Outlook and restart it normally.
  7. Enable add-ins one by one to find the one causing the issue.

Disabling add-ins helps identify if any third-party tool is interfering with Outlook’s normal operation.

Step 3: Repair Outlook Data Files

Corrupted Outlook data files can trigger error 0x80070021. Repairing them often fixes the problem.

  1. Close Outlook completely.
  2. Go to the folder C:Program Files (x86)Microsoft OfficerootOffice16 (the location might vary depending on your Office version).
  3. Find and run the tool SCANPST.EXE.
  4. Click Browse and select your Outlook data file (.pst or .ost). You can find it in C:Users[YourUsername]DocumentsOutlook Files or C:Users[YourUsername]AppDataLocalMicrosoftOutlook.
  5. Click Start to begin scanning.
  6. If errors are found, click Repair.
  7. Once done, open Outlook and check if the error persists.

This tool fixes issues inside your data files that may prevent Outlook from working properly.

Step 4: Change Registry Settings to Fix File Locking

Error 0x80070021 can happen if Windows locks certain files used by Outlook. Adjusting the registry can resolve this.

Important: Editing the registry incorrectly can cause serious problems. Follow these instructions carefully, and consider backing up your registry before proceeding.

  1. Press Windows + R, type regedit, and press Enter.
  2. Navigate to this key:
    HKEY_LOCAL_MACHINESystemCurrentControlSetServicesWebClientParameters
  3. Find the value named FileOpenCacheLifetimeInSec.
  4. Double-click it and change its value to 0 (zero).
  5. If the value does not exist, right-click on the right panel, select New > DWORD (32-bit) Value, name it FileOpenCacheLifetimeInSec, and set it to 0.
  6. Close Registry Editor and restart your computer.
  7. Open Outlook again to test if the error is fixed.

This step prevents Windows from locking files that Outlook needs, which is a common cause of the error.

Alternative Method: Run Outlook as Administrator

Sometimes permission issues cause this error. Running Outlook with administrator rights can help.

  1. Right-click the Outlook shortcut on your desktop or Start menu.
  2. Select Run as administrator.
  3. Check if the error still appears.

If this solves the problem, you can set Outlook to always run as administrator by right-clicking the shortcut, choosing Properties > Compatibility, and checking Run this program as an administrator.

FAQs

What causes Outlook error 0x80070021?

This error commonly occurs when Outlook files are locked by other programs, corrupted data files exist, or conflicts with add-ins or system permissions happen.

Can antivirus software cause this error?

Yes, some antivirus programs lock files or interfere with Outlook processes. Temporarily disabling your antivirus can help identify if it’s causing the problem.

Is it safe to edit the Windows registry?

Editing the registry should be done carefully. Always back up the registry before making changes to avoid system issues.

Will repairing Outlook data files delete my emails?

No, the repair tool fixes errors without deleting your emails or data. However, it’s always good to keep backups.

Can I fix this error without technical help?

Yes, the steps provided are designed for users with basic computer skills. Follow instructions carefully, and you can fix the error yourself.

When Nothing Works

If you have tried all the steps above and Outlook error 0x80070021 still appears, consider the following options:

  • Create a new Outlook profile: Sometimes, profiles get corrupted and cause errors.
  • Reinstall Microsoft Office: A fresh installation can fix deeply rooted problems.
  • Contact Microsoft Support: Visit the official Microsoft support website for personalized help: Microsoft Outlook Support.
  • Use Microsoft’s automated repair tools: Microsoft offers tools like the Support and Recovery Assistant to diagnose and fix Outlook issues automatically.

Conclusion

Outlook error 0x80070021 can be frustrating but is usually fixable with simple troubleshooting steps. Start by closing conflicting programs and disabling add-ins to rule out basic issues. Repairing your Outlook data files and adjusting registry settings can solve more complex causes.

Always proceed carefully when editing the registry and keep your system updated to prevent future errors. If all else fails, creating a new profile or reinstalling Office can help.

By following this guide, you should be able to fix the error and enjoy smooth Outlook performance on Windows 11.

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