Blind carbon copy is used in email when you are sending the same message to many people at the same time. When you use BCC, it prevents the recipients from seeing each others email addresses.
Why is BCC important?
First of all, it's common courtesy. Unless you know that your recipients want to expose their email address to each other, you should address the individuals using blind copy.
It also minimizes spam and viruses. Even though nobody on your list may be a spammer or a virus writer, their computer may be infected with a virus that collects all the email addresses in their incoming mail. When you do not BCC, there is an increased possibility that your list recipients will see more spam (and possibly more viruses) coming their way.
I do want to hear about upcoming gigs and other news from people I know but I don't want to get more spam and/or virus attacks. Most people feel the same way.
How Do I BCC?
All email programs have a way of sending your message using BCC:. You put the email addresses in exactly the same way, but instead of putting all the email addresses on the TO: line, you put them on the BCC: line.
You might have to dig around in your email program to make the BCC: line appear. For instance, Microsoft Outlook gives you a chance to use BCC: once you have opened up your contacts or address book.
What about the TO: line? My email program requires something there!
If your email program or your ISP won't send an email with an empty TO: line, put your own email address there. Put everybody else on the BCC: line.
What About Carbon Copy (CC)?
Nope. CC does not hide the recipients email addresses from each other. It's basically just the same as putting the email addresses on the TO: line. Don't do it.