Internet DRAFT - draft-grandhi-pc-smtp
draft-grandhi-pc-smtp
Internet-Draft The "Pc" field for SMTP Gururaja Grandhi
Hewlett-Packard Company
Expires: November 12, 2005 May 12, 2005
The "Pc" field for SMTP
draft-grandhi-pc-smtp-01.txt
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Copyright Notice
Copyright (C) The Internet Society (2005). All Rights Reserved.
Abstract
This draft specifies a mechanism by which an SMTP sender can send
a copy of mail to multiple recipients, with out exposing other's
mail address to recipient and vice versa.
1. Introduction
Currently if a sender wants to send a message to multiple addresses
without exposing the other's mail address, then the sender uses the
"Bcc" field in the Mail header to hide the identities marked in the
"Bcc" field. The recipients of the mail marked under "Bcc" list will
not either have his mail address in the "To" or "Cc" list. Sometimes
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there is a high chance that this mail gets ignored by the recipient
as he is not addressed directly and it is just a blind carbon copy.
This draft specifies a mechanism through which a sender can send a
copy of message to multiple recipients with a special field in the
Mail header, which would interpreted by the SMTP server as "To" list,
however protecting their identities from others in the mail
communication (something like members in Bcc field and without
affecting the other fields in the mail header).
2. Conventions Used in this Document
The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD
NOT", and "MAY" in this document are to be interpreted as described
in "Key words for use in RFCs to Indicate Requirement Levels"
[KEYWORDS].
3. Requirement
The requirement is to provide the user a new field "Pc", that
achieves the similar functionality as that of a "Bcc" field.
However, the "Pc" recipients of this message will be treated as
primary recipients.
4. Header Updates
A new field needs to be added into the SMTP header [RECEIVER FIELDS]
called "Pc". The SMTP server would ensure to use a member of the "Pc"
list as "To" list while delivering to SMTP receiver, however
protecting his/her identity to others and vice versa.
The intermediate MTAs which does not support "Pc" field will
ignore the "Pc" field, which MAY cause the "Pc" field recipient
not receiving the mail.
5. Format of the Field
The format specification of this field should be treated as
a "Cc" field. This field would be a part of the header and
would be carried forward throughout the mail thread.
6. Processing of the "Pc" Field
Client: The client must treat the "Pc" field as similar to "Cc"
field while sending the mail to SMTP servers. The "Pc" list should
be added in the Mail header before sending the mail.
Server: The "Pc" field MUST be processed only at the final receiver's
SMTP servers. Before storing the received message in the message
store, for each of the users in the Pc field, the corresponding
mail address MUST be appended to the "To:" list of the message.
The remaining mail addresses in the "Pc" list SHOULD be ignored. All
the remaining fields like To,Cc,Bcc SHOULD be the same in the mail.
The "Pc" field MUST be processed after the alias [ALIAS] has been
expanded. If an alias is in the "Pc" list, all the members of the
alias [ALIAS] should get the ALIAS name in the "To:" list.
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Relay/Gateway: The Relay/Gateway SHOULD just forward the "Pc"
field as it is to the next Relay/Gateway.
7. Formal Syntax
The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) notation as specified in [ABNF]. This syntax reuses the
appropriate formal syntax defined in the INTERNET MESSAGE FORMAT
Pc = "Pc:" address-list CRLF
CRLF = Carriage return (CR, ASCII value 13) and
Line feed (LF, ASCII value 10)
address-list = (address *("," address)) / obs-addr-list
address = mailbox / group
mailbox = name-addr / addr-spec
name-addr = [display-name] angle-addr
angle-addr = [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr
CFWS = *([FWS] comment) (([FWS] comment) / FWS)
FWS = ([*WSP CRLF] 1*WSP) / ; Folding white space
obs-FWS
obs-FWS = 1*WSP *(CRLF 1*WSP)
ctext = NO-WS-CTL / ; Non white space controls
%d33-39 / ; The rest of the US-ASCII
%d42-91 / ; characters not including "(",
%d93-126 ; ")", or "\"
ccontent = ctext / quoted-pair / comment
comment = "(" *([FWS] ccontent) [FWS] ")"
addr-spec = local-part "@" domain
local-part = dot-atom / quoted-string / obs-local-part
domain = dot-atom / domain-literal / obs-domain
domain-literal = [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]
dcontent = dtext / quoted-pair
dtext = NO-WS-CTL / ; Non white space controls
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%d33-90 / ; The rest of the US-ASCII
%d94-126 ; characters not including "[",
; "]", or "\"
group = display-name ":" [mailbox-list / CFWS] ";"
[CFWS]
mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
address-list = (address *("," address)) / obs-addr-list
obs-addr-list = 1*([address] [CFWS] "," [CFWS]) [address]
(([FWS] comment) / FWS)
CFWS = *([FWS] comment) (([FWS] comment) / FWS)
FWS = ([*WSP CRLF] 1*WSP) / ; Folding white space
obs-FWS
WSP = space (SP,ASCII value 32) and horizontal tab
(HTAB, ASCII value 9) characters
obs-FWS = 1*WSP *(CRLF 1*WSP)
8. Reply Mail headers
The reply mail header will be similar to the recipient who had
received mail through "Bcc" field.
9. Security Consideration
The intermediate MTAs which does not support "Pc" field will
ignore the "Pc" field, which MAY cause the "Pc" field recipient
not receiving the mail.
There will not be any impact on Spam filters with this new field
addition because, for an recipient, "Pc" field is equivalent to
"To" and existing filters should work as it is.
10. Example
A wants to send a mail to the people B,C,D with out any of them
knowing about the other mail addresses.
From: A
To: X
Pc: B,C,D
CC: Y
Subject: TEST
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Recipient X's mail looks like:
From: A
To: X
CC: Y
Subject: TEST
SMTP server capable of delivering the mail to B will append the
mails "To" list with B.
Recipient B's mail looks like:
From: A
To: X,B
CC: Y
Subject: TEST
Recipient C's mail looks like:
From: A
To: X,C
CC: Y
Subject: TEST
Recipient D's mail looks like:
From: A
To: X,D
CC: Y
Subject: TEST
Recipient Y's mail looks like:
From: A
To: X
CC: Y
Subject: TEST
Appendices
A. References
The following documents contain definitions or specifications that
are necessary to understand this document properly:
[ALIAS] J. Klensin, "Simple Mail Transfer
Protocol", RFC: 2821, April 2001.
[RECEIVER FIELDS] Crocker, D., "Standard for the format of
ARPA Internet Text Messages", RFC 822,
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August 1982.
[KEYWORDS] Bradner, S., "Key words for use in
RFCs to Indicate Requirement Levels",
BCP 14, RFC 2119, March 1997.
[INTERNET MESSAGE FORMAT] P. Resnick, "Internet Message Format",
RFC 2822, April 2001.
[ABNF] Crocker, D. and P. Overell, "Augmented
BNF for Syntax Specifications: ABNF",
RFC 2234, November 1997.
Author's Address
Gururaja Grandhi
Hewlett-Packard,
29, Cunningham road,
Bangalore,
India 560052
gururaja.grandhi@hp.com
+91-80-2205-2884
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By submitting this Internet-Draft, each author represents that
any applicable patent or other IPR claims of which he or she is
aware have been or will be disclosed, and any of which he or she
becomes aware will be disclosed, in accordance with Section 6 of
BCP 79.
Gururaja Grandhi Expires November 12, 2005 [Page 7]
