How to clear drive space used by Apple Mail App without removing Internet Accounts? I'm no longer using the Apple Mail app built into OS X and it is consuming 20GB+ of space from old mail. However, I do use Calendars and Messages on those accounts. I unchecked "Mail" on those accounts, but that doesn't clear the space. If I try to remove the Internet Account, it warns that it will delete all my Messages (the Messages App messages), which I don't want to do.

It has been suggested that I simply delete the folder where Mail App stores the messages ~/Library/Mail/V2 and/or ~/Library/Mail/V3.

Can I safely free up space from mail messages from Mail using this method? 

Is there another method to safely do this?
Apple Mail stores its stuff by default under ~/Library/Mail/V2 and V3

You can free up space in there. (of course a Time Machine backup would be a good idea before deleting the content of these folders)