A new feature in High Sierra allows you to use Full Screen mode with Mail and then it splits the screen when you compose a new message or reply to one. So you see your mailboxes and messages on the left, and the message you are composing on the right.
Note: This is Club MacMost exclusive content. To view this video click the thumbnail below to go to the post as Patreon.com. Once there you will be able to view the video as long as you are logged into your Patreon account and a current supporter of MacMost at the "Club MacMost" or higher level.
