Office 365 (Outlook 2013) - Removing the First Line of Message Text From Inbox / Mail Folders View
1. Select the View tab from the ribbon and click on Message Preview.
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:
1 Line (This is checked as the default)
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.