In Emails Blind Carbon Copy (abbreviated BCC and sometimes referred to as Blind Courtesy Copy) refers to the practice of sending a message to multiple recipients in such a way that what they receive does not contain the complete list of recipients.

To specify the recipients, an e-mail message can contain addresses in any of the 3 following fields:

• To: Intended recipients of the message
• CC: field recipients are others whom the author wishes to publicly inform of the message ( carbon copy)
• BCC: field recipients are those being discreetly or surreptitiously informed of the communication and cannot be seen by any of the other addressees.
• In Outlook Express to show the Bcc: header in a message Click View and select “All Headers” as shown bellow.

It is common practice to use the BCC: field when addressing a very long list of recipients, or a list of recipients that should not (necessarily) know each other.

There are a number of reasons for using this feature:

• To send a copy of your correspondence to a third party (for example, a colleague) when you do not want to let the recipient know that you are doing this (or when you do not want the recipient to know the third party’s Email address).
• To send a message to multiple parties with none of them knowing the other recipients. This can be accomplished by addressing a message to oneself and filling in the actual intended recipients in the BCC field.
• When sending an e-mail to multiple recipients, you can hide their e-mail addresses from each other. This is a sensible anti-spam precaution because it avoids making a long list of Email addresses available to all the recipients (which is what happens if you put everyone's address in the To: or CC: fields). For this reason, it often makes sense to use the BCC: field for mailing lists. Some viruses also harvest e-mail addresses from users' cache folder or address book, and large CC lists may further the propagation of unwanted viruses, giving another reason to use BCC.