Dragging message from the panel with the list of messages (inbox) usually works for me.
However it is really difficult to drag messages from the panel where you read or preview the messages.
The first try to drag the subject always ends up selecting the text instead.
The second try with the text selected already does work but only if you grab the text already selected.
It is really annoying having to drag twice and then deselect the text every time you move an email.
Just realized the exact same thing happens if you want to move folders by dragging them.
It doesn’t work until you select the text of the folder.
After you do select the text of the folder you can drag it around, not sure if I should open another topic for this.