Mail Drop is a method for sending really huge attachments (which can't make it through some email gateways). The service ties into your iCloud account and is confined to the Mail app. It works this way: If an attachment is too large, it'll be uploaded to your iCloud account and a link to the file will be sent to the recipient. If the recipient is also using Mail under Yosemite, they'll see that attachment just as they would any other. Otherwise, they'll receive a link to the attachment instead. When they click that link, the attachment will download. Although attachments sent via Mail Drop can be very large, they still can't exceed 5GB per message.
What's new in Messages?
There are a couple new exciting features coming to Messages in OS X. First is the app's new tap-to-talk feature, which will let you send quick voice memos to friends and family members. Like messages in apps such as Snapchat, those snippets will be temporary and disappear within a few minutes of being read unless you choose to save them. You'll also be able to send a quick video or multiple images.
Group texting is also getting a huge overhaul. You'll be able to name group conversations (for easier reference), add and subtract users to the conversation on the fly, and leave the conversation (or hit the Do Not Disturb button) if you're getting flooded with texts. Messages also makes browsing images and video in a thread much simpler; tapping the Details button will let you see any attachments you've saved in that conversation over time.
And, as we mentioned above, you'll be able to view SMS messages from your pals if you also have an iPhone.
I know they didn't mention Game Center... is the green felt still around?
A moment of silence for green felt: Game Center on OS X now uses the same colorful bubbles that first appeared in iOS 7. You'll also find the same categories as its iOS counterpart, including challenges and turns.
We didn't hear anything about iTunes, but I noticed that there was a new icon in the dock...
iTunes does indeed have a new icon in Apple's promo materials, but we've not actually seen the new version in the flesh. Stay tuned: if Apple follows its usual patterns, we may hear more about its music offerings in the fall, including what's behind that red icon.
What about Photos on the Mac?
OS X Yosemite won't ship with a Mac version of the Photos app, but Apple did preview an early version of the program that should show up in 2015. It features many of the same improvements and user interface found in the iOS 8 version of Photos, and it sounds like it will use the iCloud storage locker to upload full-resolution copies of your images and video.
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