User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.119 Safari/537.36

Steps to reproduce:

From within XL, an Alt+f,d,e does not automatically launch a new email from Tbird, but gives an error message.

Actual results:

Error message: "General mail failure. Quit Microsoft Office Excel, restart the mail system, and try again."
When I do so, I get the same message.
I also get the same message when I try emailing the XL file via WindowsOfficeButton>Send>Email.

Expected results:

A new email should've been generated (as always happened before the most recent Tbird update). N.B.: no trouble if from Tbird I generate a new email and attach the file.

This has been resolved. See bug 1530820 comment #30.