And ? I thought I had cracked it, as Microsoft Security said I could only create an App Password, with 2 Step Security turned on ! So, I did that, created the app password, and tried it on TB Sync.......

Exactly the same :-( Will not recognise the Password as correct, and same 'Will not authenticate' Error !

Support for TBSync is provided by the add-on author and there are links on the download page for this.

But have you installed the EAS component that I understand is required to exchange? https://addons.thunderbird.net/en-us/thunderbird/addon/eas-4-tbsync/?src=userprofile

Hi Matt, TB Sync instructed me to add :

Provider for Exchange ActiveSync

If that's the Add on you mean, but still same error :-(

Sorry Matt, but where do I find the Downloads page for the links to TB Sync please ?

I have found the 'Add on Author' via the Add on Manager, but it doesn't have a Support / email option or details ?

I am probably not alone, in going to another provider, since Windows chose to end their Free Mail and Calendar apps !

I have decided to just run Thunderbird Calendar, and the Windows one, side by side, and Manually copy the Outlook content across ? Much easier than using any of these add-ons ?

But ? Thanks for your input Matt :-)

Did you miss this bit? https://addons.thunderbird.net/en-us/thunderbird/addon/tbsync/

Yes Matt :-)

I absolutely did ? Will send them an email, Many Thanks

I've been struggling with this for months. I tried it today and I connected via the Office365 option and bingo it loaded my calendar.

Change the synch time from 0 to some number of minutes, exit Thunderbird, and you should be all set.