For manually moving email data from older OS's -- Mountain Lion, Mavericks, Yosemite - to El Capitan, the thread at Apple Discussions website does not have a consensus on how to do this. https://discussions.apple.com/thread/7312611?start=0&tstart=0 Any guidance from the MacRumors community on how to manually migrate emails from earlier versions of OSX? (in my case, Mountain Lion). I'm wanting to migrate my Mountain Lion Apple mail to El Capitan. Sure, I could set up the IMAP accounts from scratch, but that would take a long time to download. And Apple IMAP has this crazy trait that the contents of a folder won't download unless you open the folder manually. Why can't I just say, "download everything". Why must I manually open each folder to instigate the downloading. It's crazy. I just want a complete record of emails on my hard disk for offline use.