Do You Know Email’s “BCC” Header?

There are a number of stories going around at the moment relating to unintentional release of email addresses in terms of allowing third parties access to the email addresses. This is almost always a mistake made by someone who used conventional email software (such as the standard Google Mail interface) without thinking carefully enough.

Now in most cases this does not matter too much … except possibly a brief moment of embarrassment. After all an email address is not that private, or is it?

There are two parts to why leaking email addresses even to a limited audience can be considered to be a bad thing :-

  1. People do sometimes want to keep their email address private; at the very least once an email address becomes public knowledge, spam starts arriving surprisingly quickly.
  2. Releasing an email address in association with some other piece of information can be surprisingly sensitive. If email being sent implies that the recipients are interested in HIV services, the recipients may be somewhat disconcerted to learn their membership is now effectively public.

And of course there is another reason why leaking email addresses can be a bad idea. News organisations can jump on the story as an easy way of populating their front page!

The golden rule here is if you are sending emails to more than five people who do not know each other, either use a specialised piece of software to send the emails, or use the “BCC” (Blind Carbon Copy) header.

To make things easier for people migrating from paper memos, the inventors of email used three common terms for listing addresses that email should be sent to – To (the public recipient), Carbon Copy (for public others who may be interested), and Blind Carbon Copy (for private copies). At least these terms were common in the days of formal paper memos!

The key field to remember for the purposes of this blog posting is “BCC”.

When you compose an email, you are normally given a list of fields to enter email addresses into :-


In this case (Gmail), click on the “Bcc” on the right-hand side of the “To” field and a new field will be shown :-


(The “Cc” field works in the same way)

The “Bcc” field can be filled with email addresses in the normal way, but the difference is that when someone receives the email they will not be able to see to whom it was sent.

You may think that this does not apply to you right now, but there is no harm in getting to know about “Bcc” and used to using it. It doesn’t cause any harm, and being familiar with it may save you from some embarrassment at some point in the future.

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