User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0

Steps to reproduce:

Select file(s) in Windows Explorer, right click and use "Send to ... -> Email"

Actual results:

Received a message box asking me that another application is trying to send e-mail though my user profile. Thought, that this might be new behaviour after having received the update to 60.5.2 (from 60.5.1), but after pushing "OK", it seemed that nothing has happened. However, checking the Outbox, I saw that an e-mail was sent with the attachment using no recipients and a BCC to myself (BCC configured in options for default account)

Attaching the screen shot of the dialogue so that the issue might be investigated with this dialogue as a stargin point.

Expected results:

Message composer window should have opened just as was the case earlier.

I can confirm this bug. It also disables "Share" in Office packages. If you disable "Send Do" in (MAPI) for Thunderbird in "Set Default Programs" and enable it in Outlook, "Send To" works. The moment you make Thunderbird the default for MAPI, "Send To" or "Share" in Office no longer works.

As a further comment to the above, I am running Windows 7; maybe it is related

Fixed in version 60.5.3. See release notes: https://www.thunderbird.net/en-US/thunderbird/60.5.3/releasenotes/

Also see bug 1530820 comment #30.