Hi all I updated my Thunderbird yesterday to 91.2 (32 bit). My computer is a 64 bit, if this matters. I'm on the release channel, and have never had an issue like this before, in nearly 20 years of Thunderbird use. When I want to write an email, I type the first couple of letters of the addressee into the To line. The box is surrounded with a dark highlight, and I cannot type more than 4 characters into the box... No autoprompts appear, and then nothing happens, and Thunderbird activity is suspended as (not responding).... So I tried a different tack, by replying to an email. This is fine, but I cannot add another addressee, in any of the To; CC; BCC boxes. Same scenario, 3 or 4 characters, no autoprompts, thunderbird freezes. So I tried another tack. I replied to a message, typed out my reply, without adding anybody else, and hit send. All seems to go well, and it looks like its sending, then a message pops up, Assembling Message - Done, with a blue progress line at 100%, a cancel button underneath, and a similar message in the bottom LH segment of the pane of the message itself. However, the message doesn't disappear, and the mail doesn't go. If I press cancel, the message disappears, but SEND, SPELLING and SAVE buttons are greyed out. Eventually I get a message saying Thunderbird has a problem, do I want to close the program or wait for it to respond. After waiting nearly six hours yesterday, I now just click Close the program. I run 6 different email accounts in my Thunderbird, and have done for years. I'm running the latest version of Windows 10 (very reluctant to upgrade to 11, even though I keep getting the prompts.) I'm running an HP Pavilion with a core i5 processor and 8GB of RAM, and a 256GB SSD. We are running Office 365 as our mail provider (I dislike it) but I run Libre Office rather than Microsoft products. Aaah. Just remembered - every time I open Thunderbird now, every folder and subfolder opens very irritating, as there are literally tens of sub-folders in some areas.