Office 365 (Outlook 2013 / 2016 for Win) - Removing the First Line of Message Text From Inbox / Mail Folders View
Outlook defaults to showing a preview or first line of the message content in your inbox list and other mail folders, however, there is a way to turn this off if you do not like it.
2. It will bring up a window that has the following selections:
Off
1 Line (This is checked as the default)
2 Lines
3 Lines
3. If you don't want the first line of message text to appear in your inbox (or other mail folder) view, select Off instead.
4. It will bring up a window that says, "Change preview setting in All Mailboxes or This Folder". Select your preference and your change will take effect.