Recently I have noticed that Mail.app on Mojave is sending discarded messages to the trash instead of archive. I have set the preference "Move discarded messages into archive", but that doesn't seem to make a difference. Is this a bug? According to the user guide, this setting controls the behavior "when you swipe left on a message in the message list". That description is puzzling since this is a Mac without a touchscreen.
On the toolbar, I have two separate buttons for Delete and Archive. Both of these buttons work correctly, but I like to discard messages using the delete (backspace) key.
I did figure out that setting Trash Mailbox to None will effectively make all discarded messages go to archive. But this makes it impossible to trash a message. I want the delete key to archive and I want the trash button to trash.