When you add a recipient's name to the Bcc box in an email message, a copy of the message is sent to the recipient. Any recipients added to the Bcc box will not be shown to any other recipients who receive the message. If the Bcc box does not display, you can bring it back with the steps below:
Step 1: Click "New Email" to create an email;
Step 2: In the "New Email" window, click "Options" tab and then "Bcc";
Step 3: The "Bcc" box is turned on (follow the same steps to turn it off).