Internet-Draft Ncc in Mail Header Arun Sankar Hewlett-Packard Company Expires: October 05, 2005 April 05, 2005 Ncc in Mail Header draft-arun-ncc-smtp-02.txt Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved Abstract This draft presents a mechanism to simplify one of the cumbersome aspects of mailing, when one needs to send mails only to a subset of mail-ids from an alias [ALIAS] . The basic intention is only to minimize the complication and difficulty of a mail user when a mail needs to be sent to n - m mail IDs i.e. send it to a group Id of n and exclude m from the alias [ALIAS] list. 1. Introduction The current situation is that when a mail is to be sent to an alias [ALIAS] list, there is no possible way of a negating a set of mail IDs from that list. The purpose of this draft is a solution by the addition of another field in the Mail header. The intention is to achieve this negation of a mail IDs from an alias [ALIAS]. 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" Arun Sankar Expires October 05 2005 [Page 1] Internet-Draft Ncc in Mail Header April 05 2005 [KEYWORDS]. 3. Requirement The requirement is to provide the user with a field, using which mails can be sent to a subset of an alias [ALIAS], i.e. a provision "not" to deliver the mail to a set of mail IDs from the alias [ALIAS]. 4. Header Updations A new field needs to be added into the SMTP header [RECEIVER FIELDS] called "Ncc". This would act as a negation to the To, Cc and Bcc fields and ensure the mail is not sent to the mail ID mentioned in the "Ncc" field. The Ncc field SHOULD be a part of the mail header in the implementation. This needs to be a part of the header as the alias processing could be done in any of the intermediate relay servers and the "Ncc" field needs to be available for processing. 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. The SMTP service extension for Ncc The Ncc option MAY not be implemented in all Mail Servers. This SHOULD not affect the servers that have implemented Ncc. The client can figure out if the server has Ncc implemented using the EHLO command transaction. When the client sends the EHLO command, the server responds with "NCC". E.g. S: 220 test1.example.com ESMTP server ready C: EHLO test2.example.com S: 250-test1.example.com S: 250 NCC If the server does not respond with an Ncc, the mail SHOULD not be processed further but a suitable error message like "NCC" not supported should be sent back to the sender. 6. Processing of the Ncc Field. The Ncc Field MUST be processed after the alias [ALIAS] has been expanded and before the creation of the envelope. The mail IDs in the Ncc field MUST be removed from the To, Cc and the Bcc fields during its processing. If there is an alias [ALIAS] in the "Ncc" field, it should be expanded first and then proceed with the negation of the Mail-Id's. Each recipient address from "Ncc" header field SHOULD NOT be copied to a RCPT command. Any empty fields SHOULD then be removed from the headers. Once this process is completed, the remaining headers SHOULD be checked to verify that at least one To:, Cc:, or Bcc: Arun Sankar Expires October 05 2005 [Page 2] Internet-Draft Ncc in Mail Header April 05 2005 header remains. If none do, then the From: address SHOULD to be added to the "Rcpt To" command and the mail processing could be continued. Implimentations SHOULD ensure appropriate error conditions in case the To:, Cc: and the Bcc: field gets negated and are nullified. This field MUST be treated similar to the Cc field with respect to syntax and and processing has to be done in mail gateways, relays etc. The Ncc field has to be a part of the mail envelope. Its existence in the envelope is necessary as the alias expansion can happen in any intermediate server. 7. Example A needs to send a mail to a group but the intention is not to send this to D. From: A From: A To: B To: B CC: C,E,F,G,H CC: Team_ABCDEFGH nCC: D Subject: TEST Subject: TEST On the continuation of the thread and D is still not a part of the list. From: B From: B To: A To: A CC: C,E,F,G,H CC: Team_ABCDEFGH nCC: D Subject: TEST Subject: TEST 8. Security Considerations. The most important Security point that needs to be considered in this draft is with recpect to a User-Agent that does not have Ncc implimented. This User-Agent might drop the header that it does not understand. This could result in the "Ncc" Header being dropped and even a server that supports the "Ncc" field would not be able to process the "Ncc" field in the reply. The other minor problem is when the server does not support "Ncc", which is solved by the service extention to SMTP. 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 of the Format of ARPA Internet Text Messages", RFC 822, August 1982. Arun Sankar Expires October 05 2005 [Page 3] Internet-Draft Ncc in Mail Header April 05 2005 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Author's Address Arun Sankar Hewlett-Packard, 29, Cunningham road, Bangalore, India 560052 sankar@hp.com +91-80-205-3107 9. Full Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. Arun Sankar Expires October 05 2005 [Page 4]