I am using Thunderbird to archive emails to a local folder. I have put emails in separate folders by year. Still, it took a much longer time than I expected. I guess the reason might be synchronization. Often Thunderbird download the same folder, or a set of messages in a folder, repeatedly. It is hard to tell how many messages have a local copy. One example is showing in the attached picture. It has been stuck there for a long time. Apparently, the progress bars are not drawn correctly. The lower folder is almost done by the number of messages, not the top one. Thunderbird version: 128.4.1esr. OS: Windows 11.