For this reason, you should use the BCC: field when sending a message to a large group. Each recipient will receive his or her own copy of the message, but the email addresses of the other recipients will be shielded from view.In addition, using the BCC: field to conceal email addresses acts as an anti-spam measure.If you use the TO: field or the CC: field to send a message to a large group, it becomes more likely that the recipients will receive unwanted email.. If a recipient uses the “Reply to All” option, the reply will not be sent to those individuals in the BCC: field. Occasionally an email recipient may respond to a message using the “Reply to All” feature. If you have placed a large list of recipients in the TO: or CC: field, all of them will receive the reply.