New Internet Draft: draft-ietf-uri-url-mailserver-00.txt

Paul Hoffman (
Tue, 24 Jan 1995 10:03:58 -0700

Message-Id: <v02110104ab4ae2949d79@[]>
Date: Tue, 24 Jan 1995 10:03:58 -0700
From: (Paul Hoffman)
Subject: New Internet Draft: draft-ietf-uri-url-mailserver-00.txt

IETF URI Working Group
Expires July 23, 1995

Status of This Memo

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A new URL scheme, "mailserver", is defined. It allows mail client
software to create RFC822 mail messages from a URL.


In the URL specification, RFC1738, the "mailto" scheme is defined and is
described as:

     Unlike many URLs, the mailto scheme does not represent a data
     object to be accessed directly; there is no sense in which it
     designates an object.

However, there are many resources on the Internet that can only be
accessed by mail that cannot be described by the mailto scheme. To
access such an object, the mail message must have a specified subject
and/or content. For instance, many mail response servers will return a
file if you send a mail message with the proper request.

The "mailserver" URL has the form:


Client software would prepare a mail message with the given headers and
the <body> text as the body of the message.

Thus, the "mailto" scheme will be used to give the mailing address of a
person or of a mailserver that requires no subject or message body; the
"mailserver" scheme is used to give a template that will cause the
specified resource to be returned.

Headers are given in RFC822 format, and it is likely (and probably
preferable) that only a "Subject:" header be included. Headers are given
without spaces after them, such as "Subject:current-issue".

The body text may span more than one line. Any "/" character in the body
should be interpreted by the mail client as a CRLF sequence when
translating a URL to a mail message.


A URL for a mail response system that requires the name of the file in
the subject might be:


A mail response system that requires a "send" request in the body might
have a URL that looks like:


A similar URL could have two lines with different "send" requests:


The "mailserver" scheme would also help people get another type of
Internet resource, namely mailing lists. For example:



RFC1738 requires that many characters in URLs be encoded. This affects
the mailserver scheme for some common characters that might appear in
subjects or message contents. Two such characters are space (" ", ASCII
hex 20) and forward slash ("/", ASCII hex 2F). Note the examples
above that use "%20" for space in the message body. Note further that an
unencoded forward slash in the body area (after the "//") is to be
translated by the mail client to CRLF.

People creating mailserver URLs must be careful to encode any reserved
characters that are used in the URLs so that properly-written URL
interpreters can read them. Also, client software that reads URLs must
be careful to decode strings before creating the mail message so that
the mail messages appear in a form that the recipient will understand.
These strings should be decoded before showing the user the mesage.

Specifying Headers

A mailserver URL can include headers for the client software to add to
the message. Each header is in the form:


Thus, a URL with a "Subject:" header, a "X-magic" header, and a body
might look like:


See the "Security" section below for important considerations for using

Additional BNF for RFC1738

mailserverurl    = "mailserver:" encoded822addr "/" *[header "/"]
                   "/" body
body             = [body_line] *["/" body_line]
body_line        = *[uchar]
header           = encoded822header ":" header_text
encoded822header = 1*xchar  ; further defined in RFC822
header_text      = *[uchar]


The mailserver scheme is intended to send a message from one user to
another, and thus can introduce many security concerns. Mail messages
can be logged at the originating site, the recipient site, and
intermediary sites along the delivery path. If the messages are not
encoded, they can also be read at any of those sites.

A mailserver URL gives a template for a message that can be sent by mail
client software. The contents of that template may be opaque or
difficult to read by the user at the time of specifying the URL. Thus, a
mail client should never send a message based on a mailserver URL
without first showing the user the full message that will be sent
(including all headers, including those specified in the URL), fully
decoded, and asking the user for approval to send the message. Examples
of problems with sending unapproved mail include:
- mail that breaks laws upon delivery, such as making illegal threats
- mail that identifies the sender as someone interested in breaking laws
- mail that identifies the sender to an unwanted third party
- mail that goes to an unwanted party, such as through a "cc:" or "bcc:"
- mail that causes a financial charge to be incurred on the sender
- mail that causes an action on the recipient machine that causes damage
that might be attributed to the sender

If a mailserver URL specifies headers, these headers can cause security
problems, such as identifying the sender to a malicious third party.
Further, headers other than "Subject:" can cause undefined actions in
some mail programs that may compromise security. Security-conscious mail
clients should scrutinize the headers and their contents before
including them in mail messages; some clients might even choose to
ignore some or all of the headers other than "Subject:" in a URL.

Author contact information:

Paul E. Hoffman
Proper Publishing
127 Segre Place
Santa Cruz, CA  95060 USA
Tel: 408-426-6222