The Share option in W10 currently only works with the Mail app. That may change in the future, e.g. an upcoming version of Firefox will integrate Share. For now, you can use Send to/Mail recipient from the right-click menu in File Explorer.

I just checked and although the solution given does answer why you can not use Thunderbird for Photo share, SEND MAIL IN FILE EXPLORER SEEMS TO ONLY USE WINDOWS MAIL ALSO.

Send to/Mail recipient uses TB here, so you must have TB not set as the default in some, possibly obscure, place in Windows settings. Besides under Tools/Options/Advanced/General/System Integration, Check Now... look at W10 Settings/Apps/Default apps.

If you're comfortable editing the registry, look for the value of HKEY_CLASSES_ROOT\mailto\shell\open\command. On my system, it is "C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe" -osint -compose "%1" If yours has Mail app, that might explain the difference.

Can not find any obscure settings. Even checked default apps by Protocol and by File types. Registry setting is correct, matches yours. The only thing that works is to add attachments manually when writing the email in TB.

There are plenty of users who have problems with the Send to/Mail Recipient command. Earlier versions of W10 allowed certain settings to be changed in the old style Control Panel, such as in the picture here.

What is your value for (Default) in this registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail

None of these worked for me and then I found this article. It also involve regedit. https://support.mozilla.org/en-US/questions/1241176

gr0m1t said

None of these worked for me and then I found this article. It also involve regedit. https://support.mozilla.org/en-US/questions/1241176

You've posted to a very old topic, and the fix for a broken Send to - Mail Recipient function is included in the latest version of TB, 60.6.

https://www.thunderbird.net/en-US/thunderbird/60.5.3/releasenotes/

I'm on TB 60.6. My problem was that when I selected send to email from file explorer, thunderbird wasn't recognised as my mail client. This is a new error. I have never had the problem before and following the registry editing described in the link I specified fixed it for me. I already had set up Thunderbird as my default mail client.