HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail constantly overwritten

Question

Here is my problem.

We are using Office 365 in company but we don't want the Microsoft Outlook. Our primary mail client is Mozilla Thunderbird.

The problem is that registry value set in HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail is constantly overwritten upon system start - from Mozilla Thunderbird to Microsoft Outlook.

So far i've tried to create shortcut inside shell:startup to .reg file with this contents

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail]
@="Mozilla Thunderbird"

I can't delete or disable Outlook without uninstalling whole Office 365. Also Outlook is not run by any user on any computer - still this value is changing itself...

Is there any way to prevent HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail from future edit by system?

Answer 1

Except changing it with user interface, based on my research, I found a similar thread :Register mailto protocol to custom program on Windows 10, which mentioned a sample mail client registration - To register with Default Programs / modern Default Apps.

Also, we may be able to change default mail client using group policy via create an app associations XML file and deploy your app associations XML file through GPO, for more information, you could refer to this article.

Hope that would be helpful to you.

Answer 2

Thank You all for help!

I've ended up using Office Customization Tool (https://config.office.com/) and tutorial from here (http://woshub.com/install-custom-app-office/)

Everything works now as it should.