bcc là gì

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Blind carbon copy (abbreviated Bcc) allows the sender of a message to lớn conceal the person entered in the Bcc field from the other recipients. This concept originally applied to lớn paper correspondence and now also applies to lớn gmail.[1]

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

  • Add the names in a second step to lớn each copy, without carbon paper;
  • Set the ribbon not to lớn strike the paper, which leaves names off the top copy (but may leave letter impressions on the paper).

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

  • To: Primary recipients
  • Cc: Carbon copy to lớn secondary recipients—other interested parties
  • Bcc: Blind carbon copy to lớn tertiary recipients who receive the message. The primary and secondary recipients cannot see the tertiary recipients. Depending on gmail software, the tertiary recipients may only see their own gmail address in Bcc, or they may see the gmail addresses of all primary and secondary recipients but will not see other tertiary recipients.

It is common practice to lớn use the Bcc: field when addressing a very long list of recipients, or a list of recipients who should not (necessarily) know each other, e.g. in mailing lists.[2]


There are a number of reasons for using this feature:

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  • Bcc is often used to lớn prevent an accidental "Reply All" from sending a reply intended for only the originator of the message to lớn the entire recipient list.[3] Using Bcc can prevent an gmail storm from happening.
  • To send a copy of one's correspondence to lớn a third buổi tiệc nhỏ (for example, a colleague) when one does not want to lớn let the recipient know that this is being done (or when one does not want the recipient to lớn know the third party's e-mail address, assuming the other recipient is in the To: or Cc: fields).
  • To send a message to lớn multiple parties with none of them knowing the other recipients. This can be accomplished by addressing a message to lớn oneself (or, in some gmail clients, leaving the To: field empty) and filling in the actual intended recipients in the Bcc: field.
  • To tighten the focus of an existing gmail correspondence. By "moving people to lớn BCC," a sender can remove non-essential parties from the recipient list ví that future reply-all's will not include them. It is customary to lớn include a parenthetical note indicating that certain recipients have been moved to lớn BCC. This can be done out of courtesy to lớn 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 lớn all Bcc: recipients, which often occurs in the size 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 lớn 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 lớn separately forward the original e-mail.

Depending on the particular gmail 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 lớn one sent to lớn a single addressee. The recipient does not necessarily see the gmail address (and real name, if any) originally placed in the To: line.

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

  • their real names, but not their gmail addresses, can be listed in the body toàn thân of the message, or
  • a meaningful substitute for the names can be placed in the body toàn thân of the message, e.g. '[To General Manager and members of Remunerations Committee]', or '[To the whole Bloggs family]'.

Carbon vs. courtesy[edit]

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.[4] "Cc:" and "Bcc:" mean "carbon copy" and "blind carbon copy" respectively.

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See also[edit]

  • Carbon copy


  1. ^ Stout, Chris. "DEAR NERD: Blind carbons hide addresses." Charleston Gazette (West Virginia, USA). 1998-01-18. page P5B. NewsBank record number 100F35638A890441.
  2. ^ Husted, Bill. "Bad e-mail habits can be bothersome, embarrassing". The Atlanta Journal-Constitution (Georgia, USA). 2009-08-30. page E15. NewsBank record number 103419444.
  3. ^ Boodhoo, Niala; Carey, Bridget (2009-08-25). "Be careful when you 'reply all' to lớn e-mail". Miami Herald. pp. C8. NewsBank record number 200908250100KNRIDDERFLMIAMIH_poked-08-25-09.
  4. ^ Crocker, D.; Vittal, J.; Pogran, K. T.; Henderson, D. A. (1977). "Standard for the format of ARPA network text messages". Ietf Request for Comments (RFC) Pages - Test. ISSN 2070-1721.

External links[edit]

  • US-CERT Cyber Security Tip ST04-008, "Benefits of BCC"