Cci 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 and now also applies to email.
There are a number of reasons for using this feature:
Bcc is often used to prevent an accidental "Reply All" from sending a reply intended for only the originator of the message to the entire recipient list.[3] Using Bcc can prevent an email storm from happening.
To send a copy of one's correspondence to a third party (for example, a colleague) when one does not want to let the recipient know that this is being done (or when one does not want the recipient to know the third party's e-mail address, assuming the other recipient is in the To: or Cc: fields).
To send a message to multiple parties with none of them knowing the other recipients. This can be accomplished by addressing a message to oneself (or, in some email clients, leaving the To: field empty) and filling in the actual intended recipients in the Bcc: field.
To tighten the focus of an existing email correspondence. By "moving people to BCC," a sender can remove non-essential parties from the recipient list so that future reply-all's will not include them. It is customary to include a parenthetical note indicating that certain recipients have been moved to BCC. This can be done out of courtesy to uninterested parties, or as a way of politely cutting off non-essential parties from the thread going forward.
To prevent the spread of computer viruses, spam, and malware by avoiding the accumulation of block-list e-mail addresses available to all Bcc: recipients, which often occurs in the form of chain letters.
In some cases, the 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,
their real names, but not their email addresses, can be listed in the body of the message, or
a meaningful substitute for the names can be placed in the body of the message, e.g. '[To General Manager and members of Remunerations Committee]', or '[To the whole Bloggs family]'.
