Network Working Group                                         R. Earhart
Internet Draft: URL-SMTP                                 Carnegie Mellon
Document: draft-earhart-url-smtp-00.txt                    December 1997
Expires June 1997


                         An SMTP URL Interface

Status of this Memo

   This document is an Internet-Draft.  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
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   as reference material or to cite them other than as "work in
   progress".

   To learn the current status of any Internet-Draft, please check the
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   Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe),
   munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
   ftp.isi.edu (US West Coast).

   This document suggests a proposed protocol for the Internet
   community, and requests discussion and suggestions for improvements.
   Distribution of this draft is unlimited.

   The protocol discussed in this document is experimental and subject
   to change.  Persons planning on either implementing or using this
   protocol are STRONGLY URGED to get in touch with the author before
   embarking on such a project.


Abstract

   It is occasionally useful to be able to reference a generic server to
   be used for message submission.  URLs provide a good mechanism for
   refering to arbitrary network resources.  The SMTP URL scheme allows
   a URL to specify an SMTP server, thus allowing other protocols to use
   a general ''URL to be used for message delivery'' in place of an
   explicit reference to SMTP.






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.   Conventions Used in this Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [KEYWORDS].


.   SMTP URL Scheme

   The SMTP URL follows the common Internet scheme syntax as defined in
   [BASIC-URL] except that plaintext passwords are not permitted.  If
   :<port> is omitted, the port defaults to 25.

   The specified server should not be assumed to have any services
   available other than SMTP.  Other than authentication, no protocol
   actions are implied by an SMTP URL; an SMTP URL only specifies the
   location of an SMTP service, not what to do with it (common actions
   are to use the SMTP server to verify an address, and to submit
   Internet mail).

   An SMTP URL has the following general form:

      url-smtp  = "smtp://" url-server

   "smtp" refers to the URL scheme; "://" is used to indicate a
   reference to an Internet host address.  The <url-server> element
   includes the hostname, and optional user name, authentication
   mechanism and port number.

   Note that unsafe or reserved characters such as " " or "?" MUST be
   hex encoded as described in the URL specification [BASIC-URL].  Hex
   encoded octets are interpreted according to UTF-8 [UTF8].


.   SMTP URL User Name and Authentication Mechanism

   A user name and/or authentication mechanism may be supplied.  They
   are used to perform SASL [SASL] authentication after making the
   connection to the SMTP server.  If no user name or authentication
   mechanism is supplied, then the SASL ANONYMOUS [SASL-ANON] mechanism
   is used by default.  If an authentication mechanism is supplied
   without a user name, then one SHOULD be obtained from the specified
   mechanism or requested from the user as appropriate.  If a user name
   is supplied without an authentication mechanism then ";AUTH=*" is
   assumed.

   The ";AUTH=" authentication parameter is interpreted as described in
   the IMAP URL Scheme [IMAP-URL].



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   Note that if unsafe or reserved characters such as " " or ";" are
   present in the user name or authentication mechanism, they MUST be
   encoded as described in the URL specification [BASIC-URL].


.   Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) notation as specified in [ABNF].  This uses the ABNF core
   rules as specified in Appendix A of the ABNF specification [ABNF].

   Except as noted otherwise, all alphabetic characters are case-
   insensitive.  The use of upper or lower case characters to define
   token strings is for editorial clarity only.  Implementations MUST
   accept these strings in a case-insensitive fashion.

      url-auth           = ";AUTH=" ("*" / url-enc-auth)

      url-achar          = uchar / "&" / "=" / "~"
                           ;; See [BASIC-URL] for definition of "uchar"

      url-enc-auth       = 1*url-achar
                           ;; encoded version of auth-type-name above

      url-enc-user       = *url-achar
                           ;; encoded version of login userid

      url-server         = [url-enc-user [url-auth] "@"] hostport
                           ;; See [BASIC-URL] for definition of "hostport"

      url-smtp           = "smtp://" url-server


.   Security Considerations

   SMTP URLs have the same security considerations as IMAP URLs [IMAP-
   URL].

   Clients SHOULD make the SMTP URL being used obvious to the user, as
   using an undesireable server may compromise the security of the
   user's message.










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.   Copyright

   Copyright (C) The Internet Society 1997. All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS 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.


.   References

   [ABNF] Crocker, Overell, "Augmented BNF for Syntax Specifications:
   ABNF", RFC 2234, November 1997.

      <url:ftp://ds.internic.net/rfc/rfc2234.txt>

   [BASIC-URL] Berners-Lee, Masinter, McCahill, "Uniform Resource
   Locators (URL)", RFC 1738, December 1994.

      <url:ftp://ds.internic.net/rfc/rfc1738.txt>

   [IMAP-URL] Newman, "IMAP URL Scheme", RFC 2192, July 1997.

      <url:ftp://ds.internic.net/rfc/rfc2192.txt>







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   [KEYWORDS] Bradner, "Key words for use in RFCs to Indicate
   Requirement Levels", BCP 14, RFC 2119, March 1997.

      <url:ftp://ds.internic.net/rfc/rfc2119.txt>

   [SASL] Myers, "Simple Authentication and Security Layer (SASL)", RFC
   2222, October 1997.

      <url:ftp://ds.internic.net/rfc/rfc2222.txt>

   [SASL-ANON] Newman, "Anonymous SASL Mechanism", RFC 2245, November
   1997.

      <url:ftp://ds.internic.net/rfc/rfc2245.txt>

   [UTF8] Yergeau, "UTF-8, a transformation format of Unicode and ISO
   10646", RFC 2044, October 1996.

      <url:ftp://ds.internic.net/rfc/rfc2044.txt>


.   Author's Address

   Robert H. Earhart
   Carnegie Mellon
   5000 Forbes Ave.
   Pittsburgh PA, 15213-3890

   Email: earhart+@cmu.edu


Expires June 1997



















Earhart                                                         [Page 5]