I read this and this.

Then I installed the Akonadi console:

root@tact:/home/jj5# apt-get install akonadiconsole

I opened it from K -> Applications -> Development -> Akonadi Management and Debugging Console.

Then in it I selected Agents -> Local Folders.

Then I changed: /home/jj5/.local/share/akonadi_maildir_resource_0 to my ‘important’ Thunderbird ImapMail directory.