Thunderbird - Get all emails from all folders?

Question

Mozilla Thunderbird

Greetings.

N-boxes, i.e. a lot, by clicking the "get all new messages" button, only new mail is taken from the inbox folder, from the newsletter subfolder, from the spam folder, etc. - no, i.e. until you explicitly open it on a specific account, it will not show the letters inside, although it is likely that there may be the letter you are looking for, which I actually need.

How can this be overcome?

Answer 1

Solved, the algorithm is described here