As part of the User Experience Updates previewed in Coming Soon, we redesigned some elements of the experience to include more generous spacing and padding for a cleaner, more modern look, and to make the message list easier to scan.
However, after listening to customer feedback, we know that information density and being able to see the maximum number of messages possible in the message list is a high priority for many of our customers. Because of the feedback we received through Coming Soon, we've introduced a new density option in the View tab of the ribbon.
To see tighter spacing in your message list, task list, and around the To, Cc, Bcc, and Subject lines when composing a new email message, do the following:
If you're using the Simplified Ribbon, select View > Use Tighter Spacing.
If you're using the Classic ribbon, select View, and in the Layout group, select Use Tighter Spacing.