I get my mail through gmail's IMAP server but prefer to use Tbird's interface . Thinking there might be something evil about the first msg that was waiting to be downloaded, I used gmail's web interface to review everything new since last night, deleted several msgs that had attachments, then started Tbird again.  No change.  Can't even get Tbird into the "Work offline" state because it attempts download-of-new-msgs immediately after being started.
  The only consistently effective way I have found to STOP the hung Tbird is through (Classic) Task Manager's "Processes" list, which usually shows five or six "thunderbird.exe" instances.  After selecting whichever has the largest memory allocation I click on "End Process."
  This all "feels like" a bollixed internal state.  Does Tbird store internal-state information in its own file, or is it buried in the Registry?   If I attempt restoration from a backup, which files are needed; or is that unwise?
 I see there is a mid-April update available to 115.10; would installing it reset current messed-up internal state, or will that already messy situation prevent the update?   Is there any risk of losing my Inbox, Sent, etc contents?

Since starting my Win 10 Pro computer today, Thunderbird 115.4.2 (64-bit) has been "dead in the water". When it's launched, it posts the customary "Downloading Message 1 of [N]" status report, but then hangs right there, takes 3 or 4 minutes even to (re-)populate the tabs and panes that had been open, doesn't get past the alleged first new msg even in 15 or 20 minutes. When it does populate the Inbox pane, it shows no messages newer than last night just before shutdown. Very sluggish response to cursor, too: for ex. 30 seconds from clicking on a msg title in the Inbox pane to displaying that msg, even longer to bring up Help/About (with "Not Responding" shown in its title bar.) I get my mail through gmail's IMAP server but prefer to use Tbird's interface . Thinking there might be something evil about the first msg that was waiting to be downloaded, I used gmail's web interface to review everything new since last night, deleted several msgs that had attachments, then started Tbird again. No change. Can't even get Tbird into the "Work offline" state because it attempts download-of-new-msgs immediately after being started. The only consistently effective way I have found to STOP the hung Tbird is through (Classic) Task Manager's "Processes" list, which usually shows five or six "thunderbird.exe" instances. After selecting whichever has the largest memory allocation I click on "End Process." This all "feels like" a bollixed internal state. Does Tbird store internal-state information in its own file, or is it buried in the Registry? If I attempt restoration from a backup, which files are needed; or is that unwise? I see there is a mid-April update available to 115.10; would installing it reset current messed-up internal state, or will that already messy situation prevent the update? Is there any risk of losing my Inbox, Sent, etc contents? Thanks!!!