I signed up to FastMail using the userid xxxxxxx, but after the trial period I changed my username to my actual name. I've since updated all of the saved authentication details in Thunderbird to use the updated username but I still keep getting authentication requests from Thunderbird, for the username xxxxxxx, saying:
I've completely removed my FastMail account (both IMAP email and Calendars) from Thunderbird and re-added them after closing and restarting Thunderbird, but keep getting the aforementioned authentication dialog.
Is it FastMail that's providing that username to use to connect to my FastMail calendar? How would I find out where that username is coming from?