Hi Rebel Emerald,
Do you receive the error when previewing .msg files in Windows File Explorer?

Could I know what’s the detailed version of Outlook client?
According to my research, this issue could occur when you have the 64-bit version of Microsoft Outlook installed. The Windows preview host requires a 32-bit application previewer. When 32-bit Outlook is installed, it acts as the previewer. Without 32-bit
Outlook installed, there is no previewer available for .msg files.
If this is the case for you, please double-click .msg file to open it in Outlook instead of previewing in Windows File Explorer.
If not, let’s check preview settings:
Please press Win+R, type "regedit", press Enter to open the Registry Editor and navigate to the following registry path:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\PreviewHandlers
Ensure that you can see the string value with the data 'Microsoft Windows MAPI Preview Handler':

Besides, do you set Outlook as the default mail client?
Any updates, please feel free to post back.
Regards,
Perry
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