So mail Yosemite has an elegant new Yosemite style UI but we really focused on the basics reliable synching, fast switching between mailboxes, quick fetches of your new mail the basicsIn addition to that we wanted to address a fundamental problem with email which of these days we so often want to send large attachments whether its video or large sets of photos and we end up hitting one of these, a message saying that our recipients mail server can take those large attachments. Well, were solving that problem with a technology we call Maildrop.
With maildrop instead of your message bouncing off your recipient's mail server you can elect to have the attachments sent encrypted and securely via iCloud separate from the message and it rendezvous on the receiving end. So the recipient has a Mac they get it just like before and if you have another client they get a link to securely download those attachments. Those attachments can be up to five gigs in size him and that's mail drop.