Minimal FAX address format in Internet Mail
RFC 2304

Document Type RFC - Proposed Standard (March 1998; No errata)
Obsoleted by RFC 3192
Last updated 2013-03-02
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Network Working Group                                      C. Allocchio
Request for Comments: 2304                                   GARR-Italy
Category: Standards Track                                    March 1998

              Minimal FAX address format in Internet Mail

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

IESG NOTE

   This memo describes a simple method of encoding PSTN addresses of
   facsimile devices in the local-part of Internet email addresses.

   As with all Internet mail addresses, the left-hand-side (local- part)
   of an address generated according to this specification, is not to be
   interpreted except by the MTA that is named on the right-hand-side
   (domain).

1. Introduction

   Since the very first e-mail to fax gateway objects appeared, a number
   of different methods to specify a fax address as an e-mail address
   have been used by implementors. Two major objectives for this were

     - enable an e-mail user to send faxes from his/her e-mail
       interface;

     - enable some kind of "fax over e-mail service" transport, to
       reduce the costs of fax transmissions, and use the existing
       e-mail infrastructure.

Allocchio                   Standards Track                     [Page 1]
RFC 2304               Minimal FAX address format             March 1998

   This memo describes the MINIMAL addressing method and standard
   extensions to encode FAX addresses in e-mail addresses, as required
   in reference [13]. The opposite problem, i.e. to allow a traditional
   numeric-only fax device user to access the e-mail transport service,
   is not discussed here.

   All implementations supporting this FAX over e-mail address format
   MUST support as a minimum the specification described in this
   document.  The generic complex case of converting the whole PSTN
   addressing in e-mail is out of scope in this minimal specification:
   there is some work in progress in the field, where also a number of
   standard optional extensions are being defined.

   In this document the formal definitions are described using ABNF
   syntax, as defined into [7]. We will also use some of the "CORE
   DEFINITIONS" defined in "APPENDIX A - CORE" of that document. The
   exact meaning of the capitalised words

      "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
      "SHOULD NOT", "RECOMMENDED",  "MAY", "OPTIONAL"

   is defined in reference [6].

2. Minimal Fax address

   The "service-selector" defined in section 2 of reference [13] for the
   fax service is:

      service-selector = "FAX"

   The minimal addressing for the fax service also requires support for
   a "qualif-type1" element (see section 2 of reference [13]).  This
   element is an OPTIONAL element of the fax address, but its support,
   when present, is REQUIRED:

      qualif-type1 = "/" t33-sep "=" sub-addr

   where

      t33-sep = "T33S"

      sub-addr = 1*( DIGIT )

   Thus, the minimal specification of a fax in e-mail address is:

      fax-address = fax-mbox [ "/T33S=" sub-addr ]

      fax-mbox = "FAX=" global-phone

Allocchio                   Standards Track                     [Page 2]
RFC 2304               Minimal FAX address format             March 1998

   Note:
     See section 4.1 in case multiple sub-addr per fax-mbox need to be
     specified.

   The Minimal supported syntax for global-phone (as described in
   section reference [13]) is:

   global-phone = "+" 1*( DIGIT , written-sep )

   written-sep = ( "-" / "." )

   The use of other dialling schemas for PSTN numbers (like private
   numbering plans or local dialling conventions) is also allowed.
   However, this does not preclude nor remove the minimal compulsory
   requirement to support the "global-phone" syntax as defined above.

   Any non "global-phone" dialling schema MUST NOT use the leading "+"
   between the "=" sign and the dialling string. The "+" sign is
   strictly reserved for the standard "global-phone" syntax.

   Note:
     The specification of these different dialling schemas is out of
     scope for this minimal specification.

   User specification of PSTN e-mail addresses will be facilitated if
   they can insert these separators between dial elements like digits
   etc.  For this reason we allow them in the syntax the written-sep
   element.

   Implementors' note:
     Use of the written-sep elements is allowed, but not recommended.
     Any occurences of written-sep elements in a pstn-mbox MUST be
     ignored by all conformant implementations. User Agents SHOULD
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