Everybody knows that Mail changed it format from V3 to V4, because of new SQLite database version. So, it is not works anymore to just copy mail/V3 folder to a new OS. It don't load previous mailboxes. I hate Import/Export function in Apple Mail because it exports/imports only one folder! (So you should export Inbox, Drafts, Outbox, Spam and Junk folders SEPARATELY for each mailbox and it is a headache for me, as I'm using >5 accounts and also want to store mail in mailboxes which now not available anymore). How to move mail? I even tried this: installed Sierra, transfered my mail with Migrate Assistant (But it moves other folders and settings for every software, every junk file, settings etc, so I can't choose to move mail only). Then installed OS X on fresh hard drive and moved mail/V4 folder - and even there nothing happends!!! It didn't open my mailboxes from other Sierra install!!! How to transfer mail from old OS X to a new Sierra without any junk files and settings, which Migration Assistant gives? Are there clean step-by-step way?