When we mass email a message to groups of people, if we do not do anything with the email addresses, the email addresses will be available for every recipient to see. It may not be a bad thing for a lot of people, but I prefer to hide the emails of the groups of people who receive my messages. To do that, we simply use the bcc field in Outlook: put the groups of email addresses in the bcc field. Then put your email in the To: field. Now their emails are hidden from the recipients.