You can isolate the suspicious IMAP account by removing it temporarily without removing the message data. It would be very interesting to know the size of the INBOX folder in the suspîcious account.

Thanks for the suggestion. I opened Thunderbird to check my server settings before I removed the account, and declined to log into the mail server (thus it did not actually connect to the server). TB crashed before I had a chance to remove the account. I restarted TB and removed the account just now, so I will see if that has any positive impact. This email account is a work email that I need regular daily access to? IFF it does have a noticeable impact, what's next?

The INBOX.SBD folder is 7.1 Gb, The INBOX file is ~43.5 Mb and the INBOX.msf file is ~3 Mb.

Update, after removing the IMAP account, TB still crashes with the most recent error that it cannot submit a crash report:

Thunderbird had a problem and crashed. Unfortunately the crash reporter is unable to submit a report for this crash.

Details: Expected value at line 1 column 1

IFF it does have a noticeable impact, what's next? The INBOX.SBD folder is 7.1 Gb, The INBOX file is ~43.5 Mb and the INBOX.msf file is ~3 Mb.

The INBOX file is not very big, so I think it's not the culprit. Next and most important step is the test in a new profile : https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-thunderbird-profiles#thunderbird:win10:tb128 Start TB in the new profile, set up your IMAP account and observe what happens...

Thanks, I’ll try it, as long as TB will stay running long enough to set up the new profile - it’s now crashing within seconds or minutes of opening, with that same ‘unable to send crash report’ error. I tried opening it “offline”, and it seems to run for a marginally longer time - maybe a minute or two. Running under a completely new profile should be a sufficient test to see if my existing profile is fubar. I’ll report back soon…

You don't need to start or to run Thunderbird in order to create a new profile. Consult this article to learn how to open the TB profile folder without opening Thunderbird https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_finding-your-profile-without-opening-thunderbird In the Thunderbird folder search for the profiles.ini file and open it with a text editor: In the line StartWithLastProfile=1 replace the 1 by a 0 (zero) and save the modification. Now when you launch Thunderbird the profile manager will open in a small dialogue window where you can create the new profile

https://support.mozilla.org/en-US/questions/1473512

Start Windows in safe mode. If the crashing stops then the problem is Bitdefender.

I’d already tried that, on your similar suggestion in my other post about TB crashes over at https://support.mozilla.org/en-US/questions/1473512

Interestingly enough, I had two Vipre-related software crashes two days ago, so I sent the .dmp file to them for analysis. They suggested to disable the Web Filtering module, as it appeared to be “…working a little too aggressively”. Anecdotally, this has been a rather tedious process, to say the least. Intel has also agreed/offered to warranty exchange my i9-14900KS CPU, as they believe the now infamous microcode issue with 13-14 gen CPUs could be contributory to my issues (so they’re doing the right thing, without a hard push from me). It’s supposed to arrive within the next two days, at which point I’ll be able to retest with a fresh CPU and driver install. I’ll report back in any case. Thanks again.