Before upgrading to TB91, the following steps should be done 1 export contacts, calendars, emails 2 delete profile folder in local and roaming folders 3 Uninstall TB78 4 install tb91 and create a profile 5 create accounts 6 import emails, contacts and calendars

Now you will have tb91 working like a charm.

I'm on Thunderbird 78.12.0. I reinstalled the whole OS, so there was no old profile directory to begin with.

Before upgrading to TB91, the following steps should be done 1 export contacts, calendars, emails 2 delete profile folder in local and roaming folders 3 Uninstall TB78 4 install tb91 and create a profile 5 create accounts 6 import emails, contacts and calendars Now you will have tb91 working like a charm.

That is not an official way to update, it is not even a good idea. For most poeple ist will lead to at least some loss of data. Please don't tell folks to do that!

I'm on Thunderbird 78.12.0. I reinstalled the whole OS, so there was no old profile directory to begin with.

basically Thunderbird has two default address books and as you have just established it will not allow you to delete them. Right click the two books you have imported and select properties and give them a name commensurate with what they are, imported address books from an old version, and you will not have duplicate names.

You can move contact between address book if you like, but I would just leave it as it is, but I spend almost no time in my address book, I just add people and use the auto complete addressing to find them again so the book they are in is largely irrelevant to me.

Here's what I ended up doing:

1. I clicked on an imported address book.

2. Edit -> Select All

3. I dragged the selection to the undeletable "Personal Address Book".

I did this for both imported books. They were then empty, and I deleted them.

That also works :)