What is your current e-mail handler? "Local Folder" sounds like Apple Mail's "On My Mac" folder. If so, those are e-mail messages that were downloaded from the server to your local e-mail system. If you were using something other than Apple Mail, you would need to export those messages and then import them into Apple Mail.
hey man. thanks.
i have been having a bit of an epic battle but i am now realizing that these are now shown to me in Mac Mail after having File > Import > MBox these folders from my previous Mail handler (I /tried/ using postbox)...
anyway, obviously now I can drag other mail to this Local Folder in Mac Mail since it is now there after having imported the info from elsewhere. not sure how one does this when Mail isn't showing a local folder but presumably there is a pulldown to move IMAP mail to Local.
anyway, the big, big, big thing to know here is that you can transfer LOCAL FOLDER mail from a mail handler to Mac Mail by IMPORTING. I was trying to do this with Postbox via GMail and in addition to the upload speeds being very slow, there was not way to know if the operation was completed and it /seemed/ to crash out part way through. doing this in Postbox was like eating a Peanut Butter Sandwich (heavy peanut butter) while standing in quicksand...
glad to be out of that trap.