Yahoo! Mail has support for the Blind Carbon Copy feature of email, although the field is not displayed on the message editing screen by default. Some people have a tendency to use the "Reply to All" button when replying to messages in situations when it is not warranted, and using the BCC feature prevents this from happening, as recipients of your message are unable to see who else the message was sent to. This also protects the privacy of the recipients when you want to send a mass email.
Instructions
1. Navigate in your Web browser to Mail.Yahoo.com, and log in to your account. Click the "Compose Message" button in the upper-left corner of the screen to begin creating a new message.
2. Put any email address in the "To" field of the message. Some people put their own email address in the "To" field when sending a message to undisclosed recipients.
3. Click the "Add BCC" button near the top of the message editing screen. A new field titled "BCC" appears in the window.
4. Type the email address of each person who will receive your message in the "BCC" field. Put a comma or semicolon between each address.
5. Add a subject to your message and type the text of the message.
6. Click the "Send" button when you are ready to send the message.
