The iPhone and MacBook Air are showing that I'm logged in via the same "@mac.com" In my mail account settings I've got my "@me.com" address selected as the default address on both devices. This one of many "Mac" email addresses I have but they're all connected to the same account. I've changed the default on both devices so that it's the @Mac.com address but this makes no difference.
The inbox syncs fine. Changes I make to the inbox on my laptop are reflected on the iPhone inbox within 10 seconds. The Sent box never synchronizes. Calendar events synchronize within seconds across both devices also.