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How to Solve "Unable to open MSG files in Outlook 365"?

Are you unable to open msg files in Outlook 365? Recently, it has been seen that opening MSG files that Outlook creates are easy to perform various tasks. You can use it to save email, tasks, or any event entry on your desktop or web. But sometimes, you may need help opening the MSG files with Outlook.

issue with the opening of msg file

Various third-party tools are available that can help you to open the MSG file. However, you should know how to solve this issue with your Outlook application. With the information in this article, you will know the practical solutions.

Part 1: Basic Understanding of MSG File

Before diving into the solutions, let's know what an MSG file is and what can cause the issue of not opening it appropriately.

What is an MSG file?

An MSG file is an item that includes contact, email message, appointment, or any task you create/save in Microsoft Outlook. Simply put, it keeps all the vital information regarding an item, including attachments to an email message.

The MSG file has the file extension ".msg," and you can see it in the image below:

outlook file with the msg file extension

Primarily, Outlook uses MSG files. However, other programs like Microsoft's MAPI (Messaging Applications Programming Interface) also support this file.

Common reasons responsible for MSG file cannot open

Various reasons can cause the issue of not opening the MSG file in Outlook. Some of the common reasons are listed below:

Reason 1: First, your Microsoft has been configured incorrectly.

Reason 2: When you preview the MSG file that a hexadecimal editor creates.

Reason 3: The user is trying to open the MSG file, which is already open in Outlook.

Reason 4: You won't be able to open the file if you don't have access.

Reason 5: Wrong Outlook rules can also lead to the issue of not opening the MSG file.

Reason 6: Sometimes, the issue occurs due to the antivirus program blocking the attachments.

Reason 7: You can also encounter a problem when your MSG attachment is corrupted.

Reason 8: A whole temporary folder can also restrict you from opening the MSG file.

Part 2: How To Fix MSG Files Not Opening in Outlook?

Fix 1: Change Outlook Configuration

Your current email configuration on Outlook may be causing the issue with opening your MSG file. Hence, changing it can help you.

The below steps will enable you to change the Outlook configuration:

Step 1: First, you need to open the Outlook application on your device.

Step 2: In the second step, click on the File tab.

Step 3: Select Account Settings from the Account Settings drop-down list.

select account settings from drop down

Step 4: Next, choose the email account you want to use. After that, hit the Change button.

click on the change button

Step 5: Enter your password in the Change Account window.

Step 6: Outlook will test your account settings.

After the testing, click Next.

Step 7: In the last step, hit the Finish button and Close.

Fix 2: Open MSG File With the Same Outlook Version

Undoubtedly, there are many Outlook versions available in the market. When you know the Outlook version you use to create an MSG file, use the same version to open your MSG file. It might help you if your msg files are not opening.

Remember that it is impossible to install and run two versions of Office on one device. Hence, it will leave you with two options:

Option 1: Uninstall the existing Outlook version before installing the new one.

Option 2: Install the Office on a different computer and try to open an MSG file there.

Fix 3: Open MSG File Manually

Generally, your Windows should be able to detect the MSG file format. In addition, it should change the icon to an email in File Explorer.

The image below represents the email icon in File Explorer:

mail icon of the file in file explorer

Double-click on the icon to open the file with Outlook. You can go ahead, as your Windows already has an MSG file associated with the correct application. If you can't see the email logo, your Windows might fail to detect the right app. In this situation, you can right-click on the file and move forward like the Open With > Outlook option.

choose outlook after selecting the open with

After doing this, Windows will get instructed to associate the MSG file format with the Outlook application. Therefore, you don't need to right-click on the file in the future. If you double-click the file, it will also work the same.

Fix 4: Disable 3rd Party Antivirus

An antivirus can restrict your MSG file from opening in File Explorer. One of the main reasons behind it is that your trusted antivirus has flagged your MSG files as a virus. Have you seen a notice or a pop-up on your screen to this effect from your antivirus? You can check the Action Center with the command Windows+A.

If you want the file to be safe, you can whitelist it if this is the case. In contrast, if it is not, manually scan the file and open it. As a final step, disable the antivirus temporarily and open the file.

Fix 5: Disable Outlook Add-ins

Outlook users have the facility to use add-ins. These are the integrations developed by third-party app developers. Usually, this allows the users to use different apps with Outlook. However, using add-ins can also cause various issues with your Outlook. One common issue is that you cannot open msg files with Outlook 365.

The best solution for this situation is disabling the add-ins causing the conflict. You can either disable all of them or try disabling one-by-one to check which is causing the issue.

Here are steps that will help you in disabling the add-ins:

Step 1: Open Outlook on your computer.

Go to File tab > Options.

Step 2: Select Add-Ins on the screen's left side.

At the bottom, you will see a Manage option. Moving forward, choose COM Add-Ins in the drop-down menu. Click Go.

choose com add ins and hit go

Step 3: De-select all add-ins and hit the OK button.

deselect the files and click ok

Step 4: Restart Outlook and check if the issue is occurring again.

Now, see if the MSG file is opening or not. If not, try to re-enable one add-in at a time.

Fix 6: Clean Outlook Temp Files

Removing temp files stored by Outlook applications can add life to the app. So, do not hesitate to delete the old or damaged files that might be causing the issues. Here are simple steps that can help:

Step 1: Open File Explorer by pressing Windows+E.

Now, enter the path below in the address bar.

C:\Users\%username%\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Outlook

add path to the address bar of file explorer

If the above step doesn't work, open the Registry Editor from Windows Search Windows+S. Click Ctrl+F and open the search window. Now copy the text below and enter for a search.


copy and search the text in windows search

Next, copy the folder path and address bar in the Registry Editor and paste it into the File Explorer.

Step 2: Select all the files in the folder by pressing Ctrl+A.

Click the Delete button and delete the files.

Step 3: Reboot your device and see if the MSG files are opening with Outlook.

Fix 7: Enable/Disable Unicode Format

The way you save the Outlook email file is vital. Usually, there are two ways: MSG, and Unicode or ANSI, which older Outlook versions can use later. When saving an Outlook email, save the file from Outlook Message Format-Unicode (.msg) to Outlook Message Format (.msg) in the drop-down Save as type. Also, ask the sender to resend the file in some other format.

try to enable or disable the unicode format

If your email is in Outlook, use the steps below and change the file format from MSG to MSG in ANSI or vice-versa. Change the Outlook configuration 2010 and versions after that:

Go to File > Options > Mail. Now, enable or disable the Use Unicode Format option in the Save messages part.

enable and disable the unicode format

Make changes and attempt to open the file with Outlook again. The file type you use to open and save depends on your Outlook version.

Fix 8: Update Windows and Office

Several errors can be fixed by simply updating the Windows operating system. After that, update the Office application to the latest version.

The following method can be used to update the Windows OS:

Step 1: Click Windows+I and open Settings.

Now, go to the Windows Update. Inspect the updates, and if any are available, download and install them. After successful installation, you will be asked to Restart the computer like below.

open msg after restarting the windows

Besides, automatic updates are available for Microsoft Office. By default, it is enabled in the software. But you can check it manually if you want to. Following is the simple method:

If you have an installed Office app from Microsoft Store, open it and go to the Library. Now, check for the updates for all the apps installed from the Store.

check the requirement of the update

If you have directly installed the setup file, check for the updates for individual Office applications. Below is the method that you can use:

Open Outlook and click File > Account > Update Options. Now, click Update Now from the list.

update outlook to the latest version

Fix 9: Rebuild Extend.dat File

Outlook creates a file called Extend.dat. This file may be corrupted and lead to MSG file errors. However, there is a way to force Outlook to recreate a file from scratch.

Step 1: First, close Outlook and other applications running on your device.

Click Windows+E and open File Explorer. Now, search for the extend.dat file in the search bar.

search extend dat in search bar of file explorer

Step 2: In the second step, Rename every file you find extend.old.

Choose the file, click on F2 and do the renaming. Finally, restart Outlook and try to open the MSG file.

Fix 10: Convert All Files into PST & Import them into MS Outlook

One more way is possible that can help you with the appropriate opening of your MSG file. In this solution, you can convert all your files into PST files. After the successful conversion, you can import them into Microsoft Outlook.

Fix 11: Repair Office

Windows has an in-built function for repairing and resetting applications. With the help of this, many common issues can be solved. Hence, you can repair the Office version and check if it helps.

Following are the steps that can help you;

Step 1: Press Windows+I and open Settings.

Go to Apps > Installed Apps.

go to apps and then installed apps in settings

Step 2: Find your installed Office version application.

Click on the three-dot icon. Next, select Modify.

click on three dots and select modify

Step 3: In the following pop-up, you can see two options: Quick Repair and Online Repair.

Go with the Quick repair first, as it will take less time and be adequate to work offline. If you are still unable to open msg files in Outlook, try Online Repair. It will require more time and a stable internet connection.

select from two options and hit repair

Hit the Repair button after selecting the option. As a final step, reboot your computer system and save all the open files or work.


Finally, let’s summarize the article by saying that solving the issue of not being able to access MSG files is possible. With all the fixes above, you can eliminate any conflict with your computer or Outlook. If you have also faced corruption with your Outlook, you can use the fixes above or try some online tool.