Using Blind Copy (BCC) when sending email

What is BCC

BCC (Blind Carbon Copy) or Blind copy is a way of sending email without enclosing the addresses the email was sent to. The recipient addresses in the BCC field will recieve the email, but will not be shown for those who recieve the email. If all the recipient addresses are added in the BCC field, the To field will show "undisclosed-recipients" for those who recieve the email.

Using BCC is a way of avoiding distribution of email addresses. If you send an email to several recipient addresses by using the To- and/or CC field, all those who recieve the email be able to see the other addresses the email was sent to, which can be preferred sometimes. On the other hand, if there is no special reason for enclosing the recipient addresses in the email, BCC is a way of avoiding this.

Why BCC

• Security
  When you send an email to several people so that all the recipients can see the other addresses the email was sent to, you give away your recipients email address. If one of your recipients gets infected with a worm or a virus that spreads through email it will be able to find all the recipient addresses from the email and send itself to all of them. The same might happen if the worm or virus sends the email addresses to an external spam list, so the recipients of your email may recieve a lot of spam.
  By using BCC you also avoid that all the recipient addresses follows the email if it's forwarded, which can be subject to the same problems as mentioned above.
• Archiving
  You can use the BCC to send a copy of the emails you send out to yourself for archiving purposes without advertising to the recipients that you're doing so.
• Reply
  If you expect replies from the email you send out that can contain confidential information or simply information that's just ment for you it would be a good idea to use BCC. This way you prevent the recipients from replying to all of those who recieved the email.

How to use BCC

To send a BCC you write the recipient addresses you want to send a BCC to in the BCC field. If you want to use the BCC field for all your recipients some email clients might object to not having a recipient in the To field. To avoid this problem you can put your own email address in the To field, this way you get a copy yourself which you can delete if you don't need it or keep it for archiving purposes.

Here is a small overview of how to use BCC with some commonly used email clients

Outlook Express

Outlook Express doesn't show the BCC field per default, but you can easily display it by pressing View in the meny and check off All headers.

Mozilla Thunderbird

In Mozilla Thunderbird you choose what way to send the email for each field. To send a BCC you choose BCC from the pulldown menu in the type field, as shown in the image below

Webmail

When using Webmail the BCC field is shown by default.

Pine

In Pine the BCC field is not shown by default, but by pressing Ctrl+R which shows "Rich Headers" the BCC field appears among some other choices, as shown below

Other resources

• Article about BCC by US-CERT
• Infoweb article about chain email and viruses in email (Norwegian)