Double click on .msg file in Windows explorer creates an error message

Question

When I double click on any .msg file in Windows Explorer (Win 11 25H2 - OS Build 26200.7171) the file opens in Outlook Classic but I get the following error message pop up:

If I right click on the file and click "open" instead of double clicking then the file opens in Outlook Classic without the error message.

I have set the correct defaults in default apps:

I have repaired and reinstalled office. The problem persists.

Answer 1

Hi,

Your file associations are correct, and repairing Office didn’t help because the root cause is broken MAPI registration, not file type defaults. Double-click uses a MAPI call to the default mail client, and that registration is failing.

 

What you can try is:

Running OUTLOOK.EXE /regserver to re-register Outlook’s MAPI components.

Verifying HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail has Microsoft Outlook as default.

Removing any conflicting Outlook versions.

Right-click works because it bypasses MAPI and opens via direct file association.

 

I hope this helps!

Answer 2

OUTLOOK.EXE /regserver is not visible.

I think that the following suggests that the Registry is set correctly?

There are no conflicting versions.