• An unknown error has occurred is an error message that occurs in Outlook when you're trying to send, receive, open or delete emails. The error can include 0x80040119, 0x80040600, 0x80070057, 0x800CCC67 and other codes, and it is usually due to corrupted PST files.
  • A virus might have corrupted the Outlook data files. That's more likely if your third-party anti-virus software needs updating. First, check if your anti-virus software is updated and then run a full scan.
  • We have a full list of Outlook errors and the solutions to them in our Outlook troubleshooting section.
  • Errors are not the only thing that can happen to Outlook, so if you have any other problems with it, check our Fix Outlook hub for answers.
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An error occurred is an error message that occurs for some Outlook users when sending, receiving, opening or deleting emails. That error message more specifically states An unknown error has occurred.

The error can include 0x80040119, 0x80040600, 0x80070057, 0x800CCC67 and other codes, and it is usually due to corrupted PST files. Here are a few tips that might fix the unknown error has occurred issue for Outlook users.

How can I fix An unknown error has occurred on Outlook?

  1. Run an Anti-Virus Scan
  2. Temporarily Switch Anti-Virus Software off
  3. Remove Microsoft Outlook Add-ins
  4. Set up a new Outlook Account Profile
  5. Fix Corrupted PST Files With the Inbox Repair Tool
  6. Fix Outlook With Third-Party Utility Software
  7. Use the Outlook 2010 Hotfix Package

1. Run an Anti-Virus Scan

A virus might have corrupted the Outlook data files. That’s more likely if your third-party anti-virus software needs updating. First, check that your anti-virus software is updated; and then run a scan with the utility.

You can usually select a check for updates option within most anti-virus utilities to update the software. For example, Avast has an Update option on its system tray context menu.

If you don’t already have a third-party utility installed, check out this software guide. Most of the more effective anti-virus utilities also have freeware versions. Alternatively, you can utilize the Windows Defender app in Windows.An unknown error has occurred Outlook Windows Defender

2. Temporarily switch anti-virus software off

Switching anti-virus software off might be a good fix for unknown errors with the 0x800CCC67 code. In which case, an anti-virus utility might be blocking the SMTP protocol. Most anti-virus utilities include a disable option of some kind on their system tray context menu.

As such, right-click the anti-virus software’s system tray icon and select the disable option to switch the utility off. Then try sending an email from Outlook again to see if that fixed the issue.

An unknown error has occurred Outlook disable antivirus temporarily

3. Remove Microsoft Outlook add-ins

Add-ins can generate numerous Outlook errors. As such, removing the add-ins off might also fix unknown Outlook errors. This is how you can remove add-ins from Outlook.

  1. First, right-click your Outlook shortcut and select Run as administrator to open the application.
  2. Click File > Options to open the Outlook Options window.
  3. Click Add-ins to open the options shown directly below.An unknown error has occurred Outlook disable microsoft office add-ins
  4. Select COM Add-in from the Manage drop-down, and press the Go button. A new window will then open that includes a list of your add-ins.
  5. Now you can completely remove an add-in by selecting its checkbox and pressing Remove. Alternatively, deselect the checkboxes to switch the add-ins off.
  6. Press the OK button to close the window.

4. Set up a new Outlook Account Profile

Your Outlook profile might be corrupted. In which case, setting up a fresh new account profile in Outlook could feasibly fix the unknown error. This is how you can set up a new Outlook profile.

  1. First, press the Cortana button on Windows 10’s taskbar.
  2. Enter ‘Control Panel’ in the search box, and select to open the Control Panel.
  3. Click Mail 32-bit to open a Mail window.
  4. Press the Show Profiles button, and then click the Add option on the Mail dialog box to set up a new account.
  5. After setting up the new account, select the Always use this profile radio button on the Mail window.
  6. Select your new profile from the drop-down menu, and click the OK button.

5. Fix Corrupted PST Files With the Inbox Repair Tool

Fixing corrupted PST data files is one of the best general fixes for unknown errors in Outlook. Thus, Outlook includes an Inbox Repair Tool, otherwise, Scanpst.exe, to repair PST files. This is how you can scan a PST with that utility.

  1. If you’re not sure where the PST file is on your hard drive, check its path from the Mail setup window. Open the Control Panel and click Mail 32-bit to open the Mail setup settings.
  2. Next, press the Show Profiles button.
  3. Select the Outlook profile you need to fix.
  4. Click the Data Files tab, which includes the Outlook data file path. Take note of the default PST file path included on that tab.
  5. Close the Mail window, and open the Outlook Inbox Repair Tool by entering ‘Scanpst.exe’ in Cortana’s or File Explorer’s search boxes.
  6. Press the Browse button to select the PST file.
  7. Click the Start button to initiate the PST scan.

6. Fix Outlook with third-party utility software

There are numerous third-party utility applications with which you can repair Outlook‘s PST files. OutlookFIX, Outlook PST Repair, and Stellar Phoenix are three that include the PST repair tools. Stellar Phoenix has a trial version that you can repair the data file with. This is how you can fix PSTs with the Phoenix software.

  1. Click the Free Download button on this web page to save the software’s setup wizard. Install the program with the setup wizard, and open the Stellar Phoenix window.
  2. Click the Browse option on the Select PST File for the repair dialog box to select a PST to scan.An unknown error has occurred Outlook repair dialog box
  3. Press the Repair button to fix the PST file.
  4. The software then provides a preview of the repaired PST file items. You can press a Save Repaired Files button on the Home tab to save the scan the details.


An unknown error has occurred Outlook repair dialog box

You might also be interested in our article about 7 of the best PC repair and optimizer software

7. The Outlook 2010 Hotfix Package

This fix is more specifically for unknown errors with a 0x80070057 code, which usually occurs when you try to set up new profiles with the Auto Account Setup process in MS Outlook 2010. Microsoft has a hotfix package for the 0x80070057 error. However, don’t expect that hotfix to fix any other unknown error.

You can save that hotfix package to Windows by pressing the Hotfix Download Available button on this website page. Then enter an email address so that you can receive an email that includes a download link and password for the hotfix. Run the hotfix exe, enter the required password and restart Windows after the hotfix weaves its magic.

Those are some of the best resolutions for Outlook’s unknown error has occurred error messages. If further fixes are still required, check out the Support and Recovery Assistant for Office 365 that can also resolve numerous MS Outlook issues.

FAQ: Read more about Outlook errors

  • How do I fix unknown error?

Perform these steps to get rid of the error: run an Anti-Virus Scan, temporarily switch off anti-virus, remove Microsoft Outlook add-ins, set up a new Outlook Account Profile, fix corrupted PST files with the Inbox Repair Tool, fix Outlook with third-party utility software.

  • How do I fix error 0x80040201?

Start writing the address that shows incorrectly. Press the down arrow key to select an autocomplete address. Press the Delete key to delete the autocomplete address.

  • How do I fix Outlook app errors?
You can try to check if Outlook is running in compatibility mode. Find the Outlook.exe file on your computer, right-click on it and choose Properties, and then select the Compatibility tab. Remove the checks for any boxes on the Compatibility tab, then select Apply and OK. Restart Outlook for the changes to take effect.

Editor’s Note: This post was originally published in April 2019 and has been since revamped and updated in April 2020 for freshness, accuracy, and comprehensiveness.