Mail Merge is very very slow.
I have been using Thunderbird Mail Merge for years. When attempting to use it now it is very very slow. It takes over a minute to bring up the window to specify which address book to use and then takes almost a minute to send an email to each address in the book. I also noticed that the font and layout in the initial window are different than in the past. Is there a fix?
Additional System Details
- User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36
The add-on page has a support email I suggest you ask the author your questions.