Mail Saver saves messages in Mail's user mailboxes into linked Finder folders as Mail message (.emlx) files. The linked folder is configured in list view so that: The file name is the header's subject; The modification date is the header's date sent; and The file's comment is the header's To: address (for sent mail) or From: address (for received mail). A threaded mailbox is saved into sub-folders in the linked folder so that threads are preserved.
Reading these files still requires Mail, but Mail is no longer required to store and organize the messages. This avoids cluttering Mail and allows you to save mail with a relevant project and to archive mail. Saved messages can be Replied, Redirected, Forwarded, Bounced and Printed, but cannot be Junked, Deleted or Flagged. Saved messages also retain attachments, if present.