Differences between To:, Cc: and Bcc:
Robert Mah
Cc:, and Bcc:) of destinations are? Basically, what is the recipient
supposed to see in terms of header data?
I thought that Bcc: was supposed to mean that the recipient doesn't
see the other people on the To: and Cc: lines (i.e. to the person
in the Bcc:, he's the only To:). Sendmail seems to simply send the
mail, but delete the bcc: line when sending it. Is my understanding of
Bcc's semantics incorrect?
A brief explination or pointers to where I might find an explination
would be very appreciated.
Cheers,
Rob
--
---------------------------------------------------------------------
Robert S. Mah | Voice: (212) 947-6507 | "Every day an adventure,
One Step Beyond | EMail: rm...@panix.com | every moment a challenge."
Bill Starkgraf
-->Can anyone explain what the differences between these three types (To:,
-->Cc:, and Bcc:) of destinations are? Basically, what is the recipient
-->supposed to see in terms of header data?
-->
-->I thought that Bcc: was supposed to mean that the recipient doesn't
-->see the other people on the To: and Cc: lines (i.e. to the person
-->in the Bcc:, he's the only To:). Sendmail seems to simply send the
-->mail, but delete the bcc: line when sending it. Is my understanding of
-->Bcc's semantics incorrect?
-->
-->A brief explination or pointers to where I might find an explination
-->would be very appreciated.
-->
-->Cheers,
-->Rob
-->--
-->---------------------------------------------------------------------
-->Robert S. Mah | Voice: (212) 947-6507 | "Every day an adventure,
-->One Step Beyond | EMail: rm...@panix.com | every moment a challenge."
What I have seen on my Sun workstation with the mail we use is the following:
The To: are the people who the message is directed.
The cc: are the people who also receive a copy usually for info only.
The Bcc: are the people who also receive a copy for info but they are a blind
recipient. Those in the To: or cc: fields do not see who is listed in the
Bcc: field.
This is what I have seen here. If this can be changed I also would like to
know. This is only my 2 cents and I would like someone else to fully explain
how this is really implemented.
Bill
+-----------------------------------------------------------------+
| Bill Starkgraf w...@ElSegundoCA.ncr.com |
| AT&T Global Information Solutions (310) 524-5754 |
| El Segundo, CA (800) 222-8372 x5754 |
+-----------------------------------------------------------------+
Dale R. Worley
I thought that Bcc: was supposed to mean that the recipient doesn't
see the other people on the To: and Cc: lines (i.e. to the person
in the Bcc:, he's the only To:). Sendmail seems to simply send the
mail, but delete the bcc: line when sending it. Is my understanding of
Bcc's semantics incorrect?
A brief explination or pointers to where I might find an explination
would be very appreciated.
It's documented *somewhere* in the standard set of Sendmail documents
(meaning I've seen it, but I don't remember where), and is modelled on
"blind carbon copies" in traditional business memos. The Bcc:'s see
all the recipients, but the To:'s and Cc:'s do not see the Bcc:'s.
Dale
Dale Worley Dept. of Math., MIT d...@math.mit.edu
--
The shepherd drives the wolf from the sheep's throat, for which the sheep
thanks the shepherd as his liberator, while the wolf denounces him for the
same act.... Plainly the sheep and the wolf are not agreed upon a definition
of liberty. -- Abraham Lincoln
Michael J. Corrigan
Bill Starkgraf <w...@ElSegundoCA.NCR.COM> wrote:
>
>This is what I have seen here. If this can be changed I also would like to
>know. This is only my 2 cents and I would like someone else to fully explain
>how this is really implemented.
>
I believe the effect of the implementation (within e.g. sendmail)
can be conceptualized as equivalent to these two steps:
1. everybody on the To:, Cc: and Bcc: lines are rounded up into "the list
of recipients" - the list of to whom the message is to be sent.
2. what gets sent to each person in the list of recipients is the
same identical message - a message with no Bcc: header (it is just removed)
Thus the To: and Cc: recipients are unaware of the blind recipients
since the blind recipients' names in the Bcc: header are gone.
The blind recipients can see who the regular recipients are since the
To: and Cc: headers are still visible
(The way that mail can get sent to someone who is not in a header
- e.g. the blind recipients - is "through the SMTP envelope"
which is what really contains the list of recipients. The recipient
part of the envelope is usually derived from the headers - but is
a separate list of the "real" recipients)
The difference between To: and Cc: is none. It is a interpretation
convention of the message reader that these are the "primary" and
"secondary" (resp.) recipients. You could just as well put all
recipients in the Cc: line and have no (or an empty) To: line
(which would probably get removed if empty).
There are implementation variations: e.g. the MH mail program makes
two separate messages - one for the non-blind recipients (again with the
Bcc: stripped out) and a second message for the blind recipients -
with a note in the message that it is in fact blind carbon copy being
pointed out explicitly.
-mike
Marc VanHeyningen
>I thought that Bcc: was supposed to mean that the recipient doesn't
>see the other people on the To: and Cc: lines (i.e. to the person
>in the Bcc:, he's the only To:). Sendmail seems to simply send the
>mail, but delete the bcc: line when sending it. Is my understanding of
>Bcc's semantics incorrect?
Um, actually yes. You have it precisely backwards. To: and Cc:
recipients do not get to see Bcc: recipients (nor do multiple Bcc:
recipients get to see each other.)
--
Marc VanHeyningen mvan...@cs.indiana.edu MIME, RIPEM & HTTP spoken here
Steve Dorner
<mvan...@cs.indiana.edu> wrote:
> To: and Cc:
> recipients do not get to see Bcc: recipients (nor do multiple Bcc:
> recipients get to see each other.)
In practice, that is usually how it works.
The spec (RFC 822), however, allows multiple Bcc: recipients to see one
another or not, at the whim of the implementation. The only time I've
seen them actually see one another is when sendmail.mumble (mumble<8)
delivers a message without a to: field to multiple bcc: recipients on a
single machine. In this case, an "Apparently-To:" header is added for
each bcc: recipient on that machine. This is truly enormously obnoxious
behavior. I assume it's gone in sendmail 8, but I haven't checked.
--
Steve Dorner, Qualcomm Inc.
"Don't give up hope. Everyone is cured sooner or later.
In the end we shall shoot you." - George Orwell
Robert S. Mah
in comp.mail.headers and via e-mail.
Let's see if I have this strait...
Software-wise, there is no difference between the To: and Cc: fields.
They are only for human consumption.
Recipients listed in the To: and Cc: fields will not see the recipients
listed in the Bcc: field. Those in the Bcc: field may or may not be
hidden from each other, depending upon how the software is implemented.
This _is_ mentioned in RFC 821, I just read it too fast :-).
Cheers,
Rob
Barry Margolin
>Cc:, and Bcc:) of destinations are? Basically, what is the recipient
>supposed to see in terms of header data?
The difference between To and cc is that the To recipients are considered
"primary", while the "cc" recipients are "secondary". The details of this
distinction depend on the context of your mail. For instance, if the mail
makes a request, the primary recipients may be expected to act on the
request, while the secondary recipients are just being informed of it.
>I thought that Bcc: was supposed to mean that the recipient doesn't
>see the other people on the To: and Cc: lines (i.e. to the person
>in the Bcc:, he's the only To:). Sendmail seems to simply send the
>mail, but delete the bcc: line when sending it. Is my understanding of
>Bcc's semantics incorrect?
You have it backward. From RFC 822:
4.5.3. BCC / RESENT-BCC
This field contains the identity of additional recipients of
the message. The contents of this field are not included in
copies of the message sent to the primary and secondary reci-
pients. Some systems may choose to include the text of the
"Bcc" field only in the author(s)'s copy, while others may
also include it in the text sent to all those indicated in the
"Bcc" list.
Unix sendmail takes the first option in the last sentence; this simplifies
things, since it can send the same message to all recipients.
--
Barry Margolin
System Manager, Thinking Machines Corp.
bar...@think.com {uunet,harvard}!think!barmar
Randy Diffenderfer
writes:
>Can anyone explain what the differences between these three types (
>To:, Cc:, and Bcc:) of destinations are? Basically, what is the
>recipient supposed to see in terms of header data?
Just a couple more thoughts on the "differences".
Many MUA's (Mail User Agents, the front-end that the user would actually
touch) have provisions for replying to the original author of the mail, the
"From:" guy, or to all recipients, the "From:" guy and all the "Cc:" guys,
but _not_ the "Bcc:" guys. The user, in this case, is the "To:" guy. :-)
Also, "Bcc:" recipients may not be as blind as you might like. If sendmail
logging is set to a common level, and a user can see the appropriate log
file, _ALL_ the recipients are listed there with their delivery statistics!
So, if you really want privacy, print it and use a stamp. :-)))
Randy Diffenderfer
rdif...@cad.gmeds.com