No rule, not even the advanced filters in Pegasus Mail know what to move to that folder (I don't even know the implicit rule myself). That's where Pegasus Mail's "quick actions" come in handy.
Using quick actions, you can define six shortcuts (Ctrl-1 – Ctrl-6) that copy or move messages to a specific folder without asking any questions, or apply a set of filters. For my stuff folder, I have set up a quick action that moves the selected messages to that folder.
File Messages Fast with Pegasus Mail "Quick Actions"
To set up a quick action to file messages fast in Pegasus Mail:
- Go to the Reader, Messages or Folder menu (depending on where you are in Pegasus Mail).
- Select Quick actions or Quick copy/move (again, depending on the menu).
- Finally, select Define quick actions.
- Use the Define button next to any action shortcut key to edit its definition.
- Make sure Move the message into a folder is selected.
- Select a folder with the Select button.
- Click OK.
Now you can move message instantly using the keyboard shortcut of your action from anywhere in Pegasus Mail — as long as you remember which keyboard shortcut belongs to which folder...

