BCC stands for Blind Carbon Copy, is a common term which refers to sending another (along with CC) copy of the mail to the recipient. By default Outlook 2010 doesn’t show BCC pane to enter recipient email address, this post covers how to add its pane in mail compose window
For inserting a BCC (Blind Carbon Copy) pane, navigate to Options tab and click BCC. This will insert a BCC pane underneath CC box. Similarly just a click is required to conceal it back.