Date: Sat, 30 Dec 1995 02:55:19 +1100
From: Robert Elz <kre@munnari.oz.au>
Message-Id: <9512291555.23578@munnari.oz.au>
To: drums@cs.utk.edu
Subject: Re: Mandatory headers (was Making Message-ID ...)

    Message-Id: <199512291519.KAA04420@info.cren.net>
    Date: Fri, 29 Dec 1995 10:23:32 +0100
    From: conklin@info.cren.net (Jim Conklin)

    Robert, why should the requirement for a recipient be not mandatory?

Because it often conveys no useful information.   Clearly the recipient(s)
must be specified when mail is sent, but it need not necessarily be in
a header.   The existance of Apparently-To: shows just how much mail
flies around with no recipient headers (that's when sendmail adds
Apparently-To).

Further, the specs currently allow both

	Bcc:
and
	To: unnamed-recipients:;

as the recipient header, neither of which conveys any information at all.
Headers with no useful information seem like a waste of space, lets just
allow the things to be dropped.

Also, note that the other 3 mandatory headers can all be created by the
UA or MTA with no user intervention (in most systems).  The UA can use
as default the user sending the mail for From, the current time for Date,
and create a Message-Id - however it cannot create the recipient headers,
as it has no idea which of whatever recipients have been passed some other
way to receive the mail should be listed in To, Cc, or Bcc - and consequently
to add any at all automatically risks making errors.

kre