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Path: utzoo!mnetor!uunet!husc6!hao!ames!amdahl!tron
From: tron@amdahl.amdahl.com (Ronald S. Karr)
Newsgroups: comp.mail.headers
Subject: RFC976 vs. the real world...
Message-ID: <18533@amdahl.amdahl.com>
Date: Sat, 21-Nov-87 04:12:48 EST
Article-I.D.: amdahl.18533
Posted: Sat Nov 21 04:12:48 1987
Date-Received: Mon, 23-Nov-87 03:05:40 EST
Reply-To: tron@uts.amdahl.com (Ronald S. Karr)
Organization: Amdahl Coup, UTS Products Hen house
Lines: 73
Keywords: mailers are fun, I like them.

Some Introduction:

A friend and I am writing a mailer which we want to be useful in both
pure RFC822 networks and UUCP-style networks.  I also want the mailer
to be useful as a gateway between such networks.  I have, working now,
what I consider to be very powerful capabilities for aliasing,
forwarding, routing and delivery.  For these types of subsystems the
capabilities in sendmail or smail2.5 are a trivial case.

However, we have conflicting ideas concerning what to do with sender
addresses in headers.  We do, now, support the idea that a pure !-path
coming in can be left as a !-path, with the current hostname prepended
(this is optional and is a function of the destination).  However,
should I ever produce, in mail originated locally, a From: line in the
following form?

	From: localhost!username

I can see one valid reason for doing this:  if the localhost is not
within a registered domain (i.e., it is only in the .UUCP domain), then
the address is not, really, recognized outside of the UUCP zone.  It
is true that some hosts on the internet have munged there mailers to
handle this as a special case, but it is not generally the case that:

	From: username@localhost.UUCP

will work.  However, gateways appear to do a reasonable job of
transforming:

	From: path!localhost!username

into:
	From: path!localhost!username@Gateway.Do.Main

Which will, generally, work.

Another reason for using localhost!username is that many sendmail
configurations can correctly send mail in registered domains to the
internet, but can't deliver to mail in the non-registered UUCP domain.
Thus, they can send to me at uts.amdahl.com, even though I am not on
the internet, because once it gets to the internet, the nameservers
there can find a gateway that can get mail to me (the MX record for
*.amdahl.com points to sun, which knows who we are).

We would like advice on this problem.  To summarize:  should From:
header fields in the form:

	From: jqp@localhost.UUCP (J. Q. P.)

be the preferred, or only, form for sites which are in the UUCP zone
but are not in a registered domain?  Or should it be possible, or
preferred for such sites to use:

	From: localhost!jqp (J. Q. P.)

instead?  For sites which are in a registered domain, there is no
question but that:

	From: xyz@Registered.Do.Main (P. D. Q.)

should be used, of course.  (Of course somebody, somewhere, will balk
at my use of "of course" in the previous sentence.)

If this is like all other two (or few) sided issues concerning header
formats, I expect that any collection of N people knowledgable on the
subject will have at least N differing opinions on the subject, no matter
how large N is.

	tron	|-<=>-|		ARPAnet: amdahl!tron@Sun.COM
      tron@uts.amdahl.com	UUCPnet: {sun,decwrl,uunet}!amdahl!tron
-- 
[views above shouldn't be viewed as Amdahl views, or as views from Amdahl, or
 as Amdahl views views, or as views by Mr. Amdahl, or as views from his house]