The Bcc field (Blind carbon copy) is one of the most underutilized features in email programs.
Use the Bcc field when those that you are addressing the email to do not know each other and do not need to know each other's names and addresses. This practice can help cut down on unwanted email.
When you start a new email, if you don't see a Bcc address line:
The Bcc field will now be available to you for future emails, unless you repeat step 1, above, to hide it.