Looking to move my OS to Mojave from Sierra (new mac) but I am having trouble getting my emails over from mail.app. I have about 80GB of email data spread over several folders, many of which have parent and child nested folders. It used to be that one would simply copy the /user/library/mail folder from one machine to the other but I understand this is no longer the case. I cannot export the mail folders as Apple recommends because this just exports an empty MBox for every parent folder and ignores all the nested ones. I also can't use Apple's migration tool as this also moves lots of other unwated data such as previous application preferences, desktop files etc.