Previously (until Yosemite) it was possible to copy / transfer mailboxes to another Mac or restore it after a clean install by just copying the Mail folder to the Library directory. With El Capitan it seems that there has been changed something and now it ain’t possible that easy anymore. By just copying the folder back emails won’t appear in the Mail App anymore. Is there already a proper way known for backing up / transferring email boxes to another Mac (which other files do have to be copied / transferred as well)? Thanks for your feedback.