All About the BCC
BCC has traditionally meant "Blind Carbon Copy" but unfortunately these days most folks don't have any idea what a "Carbon Copy" is so increasingly we're seeing it referred to as "Blind Courtesy Copy". Whatever you want to call it the concept is the same - when you send a BCC to somebody the other recipients on the message don't see that you sent them the message. That's what the "blind" part means - it's a secret.
In the example you can see at left we're sending a message to Joe and Susan and we're CCing (Courtesy Copy) the message to Carrie and Darla. All four of those folks know that the other three were sent the message because they'll be able to see that right there in the headers of the message when they receive it.
However...we're also BCCing Alan and Chris on this message. None of the other four people will know that Alan and Chris were also sent the message. Alan will know that the other four were sent it but he will NOT know that Chris was as well. Likewise Chris will know about Joe, Susan, Carrie and Darla but will NOT know about Alan. People whom you BCC messages to are hidden from the other recipients of the message INCLUDING other people you BCC'd.
There are a couple of common scenarios for using the BCC.
The Newsletter: You're sending out an e-mail newsletter to a large group of people who don't all know each other. As a courtesy to those folks and to maintain their privacy from each other you send the message to yourself or to a bogus address like "Legal Newsletter" and BCC the message to all of the actual recipients. Each recipient will receive the message, apparently addressed only to "Legal Newsletter" and will not see any of the other recipients listed.
This can be a nice solution - it certainly protects the privacy of the recipients - however it has a notable shortcoming. Some spam filters will filter out messages without a verified recipient. Since the spam filter will see only "Legal Newsletter" in the TO field it MIGHT choose to block or filter your message.
The Snitch: The age-old use for BCC was sending a message to somebody and BCCing their boss or spouse or somebody else that you didn't want those folks to know had gotten the message. In our example above you may be saying something to Joe and Susan and you want Carrie and Darla to know you said it and you want Joe and Susan to know that Carrie and Darla know you said it. BUT unbeknownst to all of them, you're also making sure that Alan and Chris know you said it.
There are a couple of potential problems here, though. Aside from the aforementioned issue with the spam filters, which could prevent Alan or Chris from receiving the message at all, if Alan or Chris were to do a Reply All instead of a Reply they're going to blow their cover! Specifically if Alan does a Reply All his reply will go to you, Joe, Susan, Carrie and Darla. "What about Chris?" you say? Nope. Chris got BCC'd just like Alan did. Chris and Alan don't know the other were sent the message so Alan's Reply All won't go to Chris. But the damage is done nonetheless.
How Do I Use BCC?
You may have noticed that when you go to create a new e-mail message you don't see BCC listed in Outlook by default. To turn it on depends slightly upon which version of Outlook you're using. In Outlook 2003 click the View menu and you can turn on BCC from there. In Outlook 2007 click the Options tab of the Ribbon and the "Show BCC" button.
How NOT To Use BCC
I'm going to catch a bit of flack for this one I think but...I really don't like the practice of BCCing yourself. It just seems lazy and inelegant. The message you just sent should be in your Sent Items folder. It can stay there. If you REALLY must have it somewhere else it's just as easy to go to Sent Items and move it as it is to wait for your own BCC'd message to come to your Inbox and move it from there. Plus you're just needlessly swelling the size of your message store with duplicate messages. Resist.