I was looking into my users'
Library/Mail folder at some emails and was wondering why they are organised the way they are. In
~/Library/Mail/V3/Mailboxes/Friends.mbox/5EF13EFE-AB95-43A9-93BB-E01CAE8DA511/Data/ there are a number of directories numbered 0 to 9. In each of these I have a number of further numbered directories, e.g. in folder 0 there are 3, 4 and 5. Each of these has a Message folder, which in turn has the individual emails.
Is there are reason why these are not all in the same directory under the Friends.mbox directory? Is that for indexing reasons? What is the hashed directory (5EF13EFE-AB95-43A9-93BB-E01CAE8DA511) for?
I'm using El Capitan.