After reading the TLDR newsletter, I deleted it. While I read another email, the one I deleted returned to the folder. However, clicking on it did not display the contents of the email.
Checking outlook.com, the message is still in the Deleted Items folder (where Thunderbird displays them in the Trash folder) and correctly so.
Opening and closing TB, clicking on a different folder and then back on the Trash folder (causing it to re-read it) displayed the email in the folder still but now the email is displayed when clicked, as if it was never asked to delete it. I pressed delete again, this time the email was deleted both in TB and online.
