Blind carbon copy

Blind carbon copy allows the sender of a message to conceal the person entered in the BCC field from the other recipients. This concept originally applied to paper correspondence (carbon copy) and now also applies to e-mails.

In some circumstances, the typist creating a paper correspondence must ensure that multiple recipients of such a document do not see the names of other recipients. To achieve this, the typist can:

With email, recipients of a message are specified using addresses in any of these three fields:

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, e.g. in mailing lists.

There are a number of reasons for using this feature:

In some cases, use of blind carbon copy may be viewed as mildly unethical. The original addressee of the mail (To: address) is left under the impression that communication is proceeding between the known parties, and is knowingly kept unaware of others participating in the primary communication.

A related risk is that by (unintentional) use of 'reply to all' functionality by someone on BCC, the original addressee is (inadvertently) made aware of this participation. For this reason, it is in some cases better to separately forward the original e-mail.

Depending on the particular email software used, the recipient may or may not know that the message has been sent via BCC. In some cases, ‘undisclosed recipients’ placed in the To: line (by the software) shows that BCC has been used. In other cases, the message appears identical to one sent to a single addressee. The recipient does not necessarily see the email address (and real name, if any) originally placed in the To: line.

When it is useful for the recipients to know who else has received a BCC message,

The interpretation of "BCC" as "blind courtesy copy" is a backronym and not the original meaning; the historic RFC 733 has an explicit "blind carbon" annotation in its definition of the BCC header field syntax. "CC" and "BCC" mean "carbon copy" and "blind carbon copy" respectively.

Sending courtesy copies of mailing list replies also directly to the author(s) of answered message(s) is a common practice on some lists, and matches a new interpretation of "CC" as abbreviation for "courtesy copy".

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