By default, Windows 10’s Mail app displays the first line of each email in addition to the subject line. If you don’t want this preview text to show, you can easily turn it off.
Maybe you work in public places, or maybe you have nosy family and friends. Whatever the reason, if you don’t want others seeing the content of your emails, we’ll show you how to hide the preview text. Mail also has a preview pane that you can hide as well.
To disable the message preview text, click the “Settings” icon in the lower-left corner of the Mail window.
Click “Reading” on the Settings pane that slides out on the right.
In the Conversation section, click the “Show preview text” slider button so it turns light gray and reads Off.
Now, you won’t see the first line of text on every email in the list.
When you click on an email, it automatically opens in the preview pane on the right. There is no setting to turn off the preview pane, but you can hide it. Simply use your mouse to change the width of the window, decreasing it until the preview pane disappears. You will see the list of accounts and folders on the left and the list of emails on the right.
Another benefit of disabling the message preview text is that each message takes up less room in the list of email, so you see more messages at a time.