An unknown error occurred on Outlook: Here’s how to fix it

Matthew Adams
by Matthew Adams
Windows & Software Expert
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  • An unknown error has occurred in Outlook occurs when you're trying to send, receive, open, or delete emails. It can include 0x80040119, 0x80040600, 0x80070057, 0x800CCC67 and other codes.
  • A virus might have corrupted the Outlook data files. That's more likely if your third-party anti-virus software needs updating.
  • 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 or an unexpected error has occurred annoying message from Outlook.

Quick Tip

If you are tired of unknown Outlook errors and corrupted PST files, we recommend switching your email client.

Mailbird is one of our favorite alternatives to Outlook. Developers are constantly working on it, bringing new features.

You can add multiple email accounts in Mailbird and have a bird’s eye view with the unified inbox. Here’s what else is great about it.

  • Emails that don’t require immediate attention can be snoozed.
  • Perform searches through all your attachments.
  • Lookup your contacts and connect with them directly via LinkedIn.
  • Integration with Google Calendar, Dropbox, Facebook, and more.

All this is great, but what really sets it apart is the free 24/7 support that you receive as a client.



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

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

There are numerous third-party utility applications with which you can repair Outlook‘s PST files. The one that comes highly recommend is Stellar Repair for Outlook.

Fixing your PST file is easy. Once you download and install the software, you select the PST file from your computer. Then start the process by clicking the Repair button.

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.

The software can recover not only emails, but calendars, contacts, notes, and attachments.

Stellar Repair for Outlook (PST repair)

Stellar Repair for Outlook (PST repair)

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3. 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

4. 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.

5. 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.

6. 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.

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 in Outlook?

Run an Anti-Virus Scan, and even temporarily switch off anti-virus. Read this comprehensive guide to fix this problem.

  • How do I fix error 0x80040201?

Start writing the address that shows incorrectly. Press the down arrow key to select an autocomplete addressing delete it. If that doesn’t work, you can follow our step by step guide to fix this problem completely.

  • How do I fix Outlook app errors?
You can try to check if Outlook is running in compatibility mode. Remove the checks for any boxes on the Compatibility tab in Outlook Properties. 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 August 2020 for freshness, accuracy, and comprehensiveness.

Editor's Note: This article was originally published in October 2017 and was revamped and updated in August 2020 for freshness, accuracy, and comprehensiveness.