How to use the Bcc and Cc fields for email in Outlook.com
When you send an email to Outlook.com, you copy it to other recipients using Cc (copy). If you want to copy other recipients, but don’t want those recipients and their email addresses to be revealed to others who receive the message, for example, when you send an email to a group whose members don’t know each other, use Bcc (blind breakdown). Also use Bcc to prevent recipients from using Reply All to send their replies to the whole group when only you should receive those replies.
The instructions in this article apply to Outlook.com and Outlook Online.
Add Bcc or Cc recipients to Outlook.com messages
To add Bcc recipients to an email you compose on Outlook.com:
Select A new message †
Select in a new message Hidden copy to add a Bcc field to the message header. Or choose To copy to add a copy field.
Enter the email addresses of the recipients in the appropriate fields.
The letter will be copied or blindly copied to those you have indicated.