Office 365 - Outlook - Show, Hide, and View the Blind Carbon Copy (Bcc) Field
Information and links to Microsoft Support about the BCC field within Outlook.
If you add a recipient's name to the Bcc (blind carbon copy) box in an email message, a copy of the message is sent to the recipient that you specify. Any recipients added to the Bcc box will not be shown to any other recipients who receive the message.
Check out these Microsoft Support articles about how to use this Bcc feature:
*Need more help with Outlook? Then check out the Microsoft Support website for Outlook help & learning.