The mailto URL scheme
RFC 2368

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Network Working Group                                       P. Hoffman
Request for Comments: 2368                    Internet Mail Consortium
Updates: 1738, 1808                                        L. Masinter
Category: Standards Track                            Xerox Corporation
                                                           J. Zawinski
                                               Netscape Communications
                                                             July 1998

                         The mailto URL scheme

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.

Abstract

   This document defines the format of Uniform Resource Locators (URL)
   for designating electronic mail addresses. It is one of a suite of
   documents which replace RFC 1738, 'Uniform Resource Locators', and
   RFC 1808, 'Relative Uniform Resource Locators'. The syntax of
   'mailto' URLs from RFC 1738 is extended to allow creation of more RFC
   822 messages by allowing the URL to express additional header and
   body fields.

1. Introduction

   The mailto URL scheme is used to designate the Internet mailing
   address of an individual or service. In its simplest form, a mailto
   URL contains an Internet mail address.

   For greater functionality, because interaction with some resources
   may require message headers or message bodies to be specified as well
   as the mail address, the mailto URL scheme is extended to allow
   setting mail header fields and the message body.

2. Syntax of a mailto URL

   Following the syntax conventions of RFC 1738 [RFC1738], a "mailto"
   URL has the form:

Hoffman, et. al.            Standards Track                     [Page 1]
RFC 2368                 The mailto URL scheme                 July 1998

     mailtoURL  =  "mailto:" [ to ] [ headers ]
     to         =  #mailbox
     headers    =  "?" header *( "&" header )
     header     =  hname "=" hvalue
     hname      =  *urlc
     hvalue     =  *urlc

   "#mailbox" is as specified in RFC 822 [RFC822]. This means that it
   consists of zero or more comma-separated mail addresses, possibly
   including "phrase" and "comment" components. Note that all URL
   reserved characters in "to" must be encoded: in particular,
   parentheses, commas, and the percent sign ("%"), which commonly occur
   in the "mailbox" syntax.

   "hname" and "hvalue" are encodings of an RFC 822 header name and
   value, respectively. As with "to", all URL reserved characters must
   be encoded.

   The special hname "body" indicates that the associated hvalue is the
   body of the message. The "body" hname should contain the content for
   the first text/plain body part of the message. The mailto URL is
   primarily intended for generation of short text messages that are
   actually the content of automatic processing (such as "subscribe"
   messages for mailing lists), not general MIME bodies.

   Within mailto URLs, the characters "?", "=", "&" are reserved.

   Because the "&" (ampersand) character is reserved in HTML, any mailto
   URL which contains an ampersand must be spelled differently in HTML
   than in other contexts.  A mailto URL which appears in an HTML
   document must use "&" instead of "&".

   Also note that it is legal to specify both "to" and an "hname" whose
   value is "to". That is,

     mailto:addr1%2C%20addr2

     is equivalent to

     mailto:?to=addr1%2C%20addr2

     is equivalent to

     mailto:addr1?to=addr2

   8-bit characters in mailto URLs are forbidden. MIME encoded words (as
   defined in [RFC2047]) are permitted in header values, but not for any
   part of a "body" hname.

Hoffman, et. al.            Standards Track                     [Page 2]
RFC 2368                 The mailto URL scheme                 July 1998

3. Semantics and operations

   A mailto URL designates an "internet resource", which is the mailbox
   specified in the address. When additional headers are supplied, the
   resource designated is the same address, but with an additional
   profile for accessing the resource. While there are Internet
   resources that can only be accessed via electronic mail, the mailto
   URL is not intended as a way of retrieving such objects
   automatically.

   In current practice, resolving URLs such as those in the "http"
   scheme causes an immediate interaction between client software and a
   host running an interactive server. The "mailto" URL has unusual
   semantics because resolving such a URL does not cause an immediate
   interaction. Instead, the client creates a message to the designated