When I compose a new message or reply to one, sometime I need to refer to an email from someone else for information to include in my new message or response. I can't seem to click outside of the email editor to get to my other emails. I always have to cancel the email I am working on, save it, find the information I need from the other email, and then come back to my saved draft. This seems to be something new with Yosemite...?