Maybe my previous posting got lost because it does not appear on forum’s front page.
Hence I will repost again: I’m facing duplicate or even multiple e-mail addresses when saving any draft with any e-mail address, not matter if the address is already known or not, the address get’s repeatedly saved into the list of collected e-mails again and again.
Moreover, if Thunderbird saves the draft itself, it again creates a new address. I can further confirm that each time I press the save-button, the e-mail address gets saved twice in the list of collected e-mails.
I do have the latest cardbook and Thunderbird version installed.