The four basic lines in the header are:

• To - contains the Email address of the person to whom the message is being sent. The To line is the only part of the header that is required. The other parts are optional.
• Subject - contains the subject of the message being sent
• Cc - allows the sender to send multiple copies of the message
• Bcc - Blind Copy - similar to the Cc line, but, because the Bcc is not sent as part of the message, the recipient of the Email does not see who was sent a copy.