Your administrator may have set up a policy to empty items from your Deleted Items folder after they've been there for a preset number of days.
You can either let messages stay there, or you can set Outlook to automatically empty your Deleted Items folder when you sign out. When you delete a message, it's first moved to the Deleted Items folder. Or click Cancel to close the move folder window without moving the folder. Click the folder you want to move to and click Move. A window will pop up that will allow you to search for the destination folder.
Learn about junk email and phishing has more information about your Junk Email folder.