How To Change MAILTO: Protocol To OEClassic or Thunderbird? (W10CE)

As the header asks, anyone cracked how to get MAILTO: to look for a programme in the list rather than an App?
God I hate what MS have done to this edition of Windows.
I found the following online and using the first batch file I managed to at least get .eml extension to associate with a 3rd party program (OEClassic in my case).
But after using the 2nd batch file I can't get the MAILTO Protocol to look for a 3rd party programme even though the old interface does display OK.
Can anyone guide me on this?

To invoke the old "Set your default programs" interface in 1709 formulate batch files:

control /name Microsoft.DefaultPrograms /page pageDefaultProgram

To invoke the old "Associate a file type or protocol with a program" interface in 1709:

control /name Microsoft.DefaultPrograms /page pageFileAssoc

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Just in case other Control Panel applets have this happen, you can find the various page names using the Windows Dev Center's list of Canonical Names of Control Panel Items:

https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx

Unfortunately it isn't listed.

This is what I get and I have a feeling it maybe because OEClassic is a 32-bit programme...or is that not important?

No unfortunately, that's all that's offered. Strangely enough near the top of the list I easily changed .eml to be associated with OEClassic using a batch file to open the old dialog but the MAILTO: is proving to be a PITA as is the actual Default Program. I've emailed the software developer for help.

I can use mailto in Firefox and choose OEClassic, that's fixed but I still can't select it for the OS's MAILTO Protocol. It just doesn't offer any external programme at all except Outlook and/or GMail and those only because they're apps. It won't allow me to browse my Programs list.