Please start *Windows'* safe mode with networking enabled - win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode Still In Windows safe mode, start thunderbird in safe mode - https://support.mozilla.org/kb/safe-mode-thunderbird

What are your results?

It still crashes just after it seems to have checked first mailbox for mail (which happens to be Google).

I did notice, as I went to safe mode without networking first time, that it loaded up fine that time.

How long before it responds? What do you see in tools > activity manager? Do you have calendars?

Seconds. Maybe 2 seconds max.

I don't remember setting up any calendars but maybe.

There is some activity with the whirling blue circle up in top left but it soon stops.

There's just enough time to get the activity manager up and it's got one entry saying indexing messages "determining which messages to index".

I wrote > How long before it responds? and you wrote > Seconds. Maybe 2 seconds max.

So it stops responding for two seconds? Or two seconds after startup it stops responding?

I would start thunderbird offline, and a) disable global indexing at tools > preferences > general and scroll to the bottom b) if that doesn't help, then disable the message display (F8), and see if you can determine whether a specific message is causing the slowness.

Yes, sorry, it stops responding about 2 seconds after loading :)

Crashes also in offline mode at same point :(

With Thunderbird shut down, rename global-messages-db.sqlite in the profile directory

Sadly didn't make any difference :(

Is there a log file for thunderbird?

Looking at it with process monitor, the last thing it's doing is a ton of cache entries before it just stops ...

We unfortunately don't have much good data on such issues in recent years - at least according to https://mzl.la/33tp4Gx To gather more data ...

How is memory and CPU when it stops responding?

Also try starting with thunderbird.exe -console -jsconsole -offline

Sadly the console also crashes so it's hard to gather anything from it :(

Thinking I'll just have to create a new thunderbird profile and hopefully that'll work ...

... no it won't. I can't seem to log into any mailbox I create. Admittedly I hardly type passwords these days but I don't think they are wrong. It is saying it can't log in.

I had same issue on an update in April - it was related with profile files somehow, I assume. I had a backup of profile which I used it till it worked - I have keep installing old versions of thunderbird (uninstall and delete all previous data before an install) till the mail app did not crashed any-more and with that version working I have made an update in the thunderbird app. After the update from the app (from the working version to the "newest" available then) all was working.

If you do not have a profile backup - you might need to set a new profile or uninstal with clear all data and after that a fresh install (so then all accounts must be set and added again, all mails downloaded again, and so on...)

"clear all data" = on profile folder to be nothing (so all profiles you can move them on other folder/partition)

Ok, I am now creating new profile ok. Dunno what happened first time. Sigh.

try deleting everything in %APPDATA%\local\Thunderbird

I have just saw an option to downgrade. If you still have old profiles you might try downgrade (and remove auto-update function) to v68... --allow-downgrade command after downgrade

try deleting everything in %APPDATA%\local\Thunderbird

That gives a minor improvement in that it's now about 6 or 7 seconds until it crashes.

I have just saw an option to downgrade. If you still have old profiles you might try downgrade (and remove auto-update function) to v68... --allow-downgrade command after downgrade

Not sure about that, I assume v68 is still supported for the timebeing?