If you'd like to see this header supported by Mozilla, vote for bug #37028

From: "J. Moreno" 
Newsgroups: news.software.readers
Subject: Re: Mail-Copies-To draft
Date: Wed, 17 Nov 1999 12:22:13 -0500
Message-ID: <991117.mct-draft@newsreaders.com>

The proposal below mainly just documents current practice (supported by
at /least/ 13 newsreaders: AdBuster, Gnus, Hogwasher, Internews,
MacSOUP, Messenger Pro, MT-NewsWatcher, NewsHound, NewsReader.Com,
NewsWatcher, rnr, Slrn, YA-NewsWatcher -- Deja.com allows setting the
header but doesn't otherwise support it, deja.com also reports more than
600,000 articles with it mentioned).

Modified 11/16/99: "sender" has been dropped due to lack of use and
possible confusion.  No longer refers to Spencers draft but instead
[MESSFOR} and a Reference section added.  From-content has been
replaced with mailbox, to indicate that the address is a full internet
address, including a FQDN, and that it is limited to a SINGLE address
(both USEFOR and MESSFOR are going to allow multiple addresses in From
and Reply-To but it is pretty much unanimously agreed that such would
be wrong for the MCT header).  Some slight grammar changes have been
made for clarity (thanks to Alan Mackenzie).

Modifed 11/17/99: changed "affect" to "effect".

Comments?

************************************************************************
Mail-Copies-To

    This header specifies a single internet e-mail address, or one of
    several keywords.  The keywords are not case sensitive.  This 
    header only effects the initial, default settings of the message by 
    the Followup/Reply Agent and the user MUST be able to change those
    settings.

    If the keywords "nobody" or "never" are used, the agent MUST NOT set
    the message for an e-mail copy to be sent, and MUST provide a
    warning if the user tries to set it so that it will be.  If either
    the keyword "poster" or "always" is used, the agent SHOULD set the
    message to have an e-mail copy sent to the reply address, and it
    MUST provide a warning before allowing the user to change this.  If
    the content of the header is a syntactically valid e-mail address
    which does not end in ".invalid", the agent MAY set the message to
    having an e-mail copy, and if it does so it MUST initially use the
    specified address, and a warning SHOULD be issued before allowing
    the user to change it.

    The presence or absence of this header MUST NOT have any effect
    when a reply is sent by e-mail instead of posted.  This header MUST
    effect only e-mail copies of followups and the agent SHOULD allow
    the user to send a copy or not regardless of this header. When a
    copy is e-mailed, the agent SHOULD indicate in the message that it
    was both mailed and posted.  If the header is not present the agent
    SHOULD NOT set the message to be both posted and mailed. The user
    may do so, but a warning is not necessary before allowing this.

===============
Notes 

This describes what several UseNet news readers are doing with the
Mail-Copies-To header.

Following the format in [MESSFOR], the syntax is specified as:
   copy-addr              = name-addr / addr-spec
   Mail-Copies-To-content = copy-addr / "nobody" / "never" /
                             "poster" / "always"

    NOTE: This differs from From-content used by MESSFOR by only 
          allowing a single address and by exluding "obs-mailbox".
          As defined by MESSFOR, addr-spec requires a FQDN.

The keywords "never" and "always" are included for legacy reasons, and
because they may be directly entered by the user, but the keywords
"nobody" and "poster" are preferred and SHOULD be used instead.

There are two methods for "indicating in the message that it was both
mailed and posted". One is to use a header field (at the time of this
writing Posted-And-Mailed is proposed with a content of either yes or
no).  The other method is to insert a note as the first line(s) of the
message, and if this method is used the line(s) MUST be inserted into
both the news and mail messages. Both usages are equally valid, and it
appears the compromise may be to do both.

Rationale

The reasons for allowing an address are to allow the poster to specify a
special address as a destination for copies of posted replies and to
allow people posting with an invalid address to specify a valid address
to which to send a Cc.  Only one address is allowed, so as to limit the
potential for abuse.

Note on Compatibility

The agent MUST NOT generate and post anything but an e-mail address or
one of the specified keywords (this does not imply any additional
validation of headers entered directly by the user).

References:

[MESSFOR]
Network Working Group Internet-Draft                                  
Internet Message Format Standard     

-- 
John Moreno