Here’s a feature I bet you didn’t know existed in Outlook (but does in Word): the ability to split the screen of your reply email in half. You can lock a portion of the original email you are replying to for easy reference as you are composing your response. The bottom half “preview” is also read-only so you don’t inadvertently edit anything.
But this “Split” command is nowhere to be found. You have to customize the Quick Access Toolbar (QAT) to get it. So right-click anywhere in the Ribbon and select “Customize Quick Access Toolbar…”:
The Split command is in the All Commands group. Clicking it gives you split screen, rockin’ action: