Thunderbird Not Displaying HTML Emails After Enigmail Install & Uninstall

OMG.
Thank you Patrick, who chimed in on this thread. The problem of Thunderbird not displaying html emails was driving me a bit batty.

The following command fixes Thunderbird’s html email viewing abilities, particularly useful after an install and uninstall of the PGP-supporting email encryption add-on Enigmail.

Menu: View > Message body as > Original HTML