Mail on Yosemite is also updated with a new Markup feature for annotating content as well as Mail Drop, which allows you to send attachments up to 5GB over email using iCloud.
Messages can now receive SMS text messages from your iPhone and an added microphone button allows you to send voice messages to other Yosemite users as well as iOS 8 users. The whole app is redesigned with the iOS iMessage look and feel. Messages on Yosemite also allows you to view shared locations of family and friends similar to the iOS Find My Friends app.
Finally, Spotlight is overhauled on OS X Yosemite with more search results from sources like Wikipedia, Bing, Maps and more which include movie times and news with interactive previews.