How to Fix the Unknown Error 0x80040600 in MS Outlook

This guide offers a detailed explanation of the unknown error 0x80040600 in MS Outlook, exploring its causes and providing step-by-step solutions. Additionally, it includes software recommendations, answers to frequently asked questions, and essential tips.

Nene Aly

By Nene Aly / Updated on March 7, 2024

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MS Outlook, a popular email client, encounters various errors that can disrupt its smooth functioning. One such error is the unknown error with code 0x80040600, which can occur during send/receive operations or when opening Outlook. This error can cause inconvenience and hinder productivity. In this guide, we will delve into the causes of this error and provide proven solutions to fix it.

Understanding the Unknown Error 0x80040600

The unknown error 0x80040600 is typically associated with problems in the Outlook Data File (.pst). This error can manifest in different ways:

  • Outlook crashes with an error message.
  • The send/receive operation fails.
  • Unable to open Outlook.

Now, let's explore some potential causes for this error.

Potential Causes of the Unknown Error 0x80040600

1. Oversized Outlook Data File: An excessively large .pst or .ost file can lead to this error. As the file size reaches or exceeds the set limit, Outlook faces difficulties in handling it.

2. Corrupted Outlook Profile: If the Outlook user profile gets damaged or corrupted, it can trigger the unknown error 0x80040600. This corruption can occur due to abrupt system shutdowns, malware attacks, or improper Outlook termination.

3. Conflict with Installed Add-ins: Conflicting or outdated add-ins within Outlook can cause errors, including the unknown error 0x80040600. These add-ins may interfere with the normal functioning of Outlook, leading to send/receive issues or crashes.

Solutions to Fix the Unknown Error 0x80040600

Solution 1: Resize the Outlook Data File

To solve the unknown error 0x80040600 caused by an oversized Outlook Data File, follow these steps:

  1. Open MS Outlook and navigate to the File tab.
  2. Select Account Settings and choose Account Settings from the drop-down menu.
  3. In the Data Files tab, select the affected data file and click on Settings.
  4. Click on the Advanced tab and click on Compact Now.
  5. Wait for the process to complete and click OK.

By compacting the Outlook Data File, you can reduce its size and potentially resolve the error.

Solution 2: Repair the Outlook Profile

If a corrupted Outlook profile is causing the error, repairing the profile can help. Follow these steps:

  1. Close MS Outlook completely.
  2. Open the Control Panel and navigate to Mail.
  3. In the Mail Setup dialog box, click on Show Profiles.
  4. Select the affected profile and click on Properties.
  5. In the Data Files tab, click on Open File Location.
  6. Locate the corresponding .ost or .pst file and rename it.
  7. Launch MS Outlook, and it will create a new profile.

Your new profile should circumvent the unknown error 0x80040600 caused by a corrupted profile.

Solution 3: Disable Conflicting Add-ins

To eliminate add-in conflicts triggering the unknown error 0x80040600, disable or remove installed add-ins. Here's how:

  1. Open MS Outlook and go to File.
  2. Select Options and choose Add-Ins from the left menu.
  3. In the Manage dropdown menu, select COM Add-ins and click on Go.
  4. Uncheck all the add-ins listed and click OK.

Restart MS Outlook and observe if the error persists. If not, gradually enable the add-ins to identify the conflicting one.

Frequently Asked Questions (FAQ)

Q: How can I prevent the unknown error 0x80040600?

A: To prevent this error, regularly perform the following actions:

  • Maintain a moderate size for your Outlook Data File (.pst).
  • Keep your Outlook profile updated and repair it if necessary.
  • Ensure that all installed add-ins are compatible and up to date.

Q: Can the unknown error 0x80040600 be caused by a virus?

A: While it is possible for malware or viruses to cause this error, it is more commonly associated with issues mentioned earlier, such as oversized data files or corrupted profiles.

Q: Is there a built-in repair tool in MS Outlook?

A: Yes, MS Outlook provides a built-in repair tool named SCANPST.EXE to fix minor issues in Outlook Data Files.


The unknown error 0x80040600 in MS Outlook can arise due to factors like oversized data files, profile corruption, or conflicting add-ins. This comprehensive guide has provided detailed solutions to resolve this error, such as resizing the data file, repairing the profile, and disabling add-ins.

Nene Aly
Nene Aly · Editor