I'm trying to transition from Apple Mail to Airmail. In Apple Mail I have some old email accounts "archived" as local "on my mac" folders; the top level folder is the name of the account (e.g. xyz.edu and abc.com), and each top-level folder has subfolders with the usual standard names (such as "inbox", "sent", etc...). When I import these into a "local" account in Airmail, airmail seems to flatten the tree and merge subfolders with the same name together.