Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!ncar!midway!gargoyle!chinet!les
From: les@chinet.chi.il.us (Leslie Mikesell)
Newsgroups: comp.mail.misc
Subject: Re: Which headers may Sendmail re-write?
Message-ID: <1990Dec18.071226.20809@chinet.chi.il.us>
Date: 18 Dec 90 07:12:26 GMT
References: <1990Dec13.131236.25304@mp.cs.niu.edu> <1990Dec16.203543.22769@chinet.chi.il.us> <1990Dec17.183615.3887@mp.cs.niu.edu>
Organization: Chinet - Public Access UNIX
Lines: 94

In article <1990Dec17.183615.3887@mp.cs.niu.edu> rickert@mp.cs.niu.edu (Neil Rickert) writes:

>  For example, you have the Internet name 'chinet.chi.il.us'
>and the UUCP name of 'chinet'.  Your system is prbably set up well
>enough to recognize both names as local.  But not all systems are.
>Suppose you didn't recognize 'chinet.chi.il.us' as local.  Then if I
>leave 'To: les@chinet.chi.il.us' on the header, and you reply to all
>header addresses, your mailer wouldn't recognize the address as local
>so would send it back to a relay for reinterpretation.

> If you were a UUCP neighbor of mine, I would automatically rewrite
>'chinet.chi.il.us' as 'chinet.UUCP' on all header destined for you, until
>I was sure you could properly recognize the address as local.

Hmmm, I thought that the big argument for having a registered domain
name was that it gave you an absolute address (i.e. interpreted the
same everywhere).  If the gateways are going to eat the names on the
way out that concept sort of disappears.  Besides, "real" uucp machines
won't understand "machine.uucp" as their own names either.

But, let's look at something a little more complicated, where the domain
name actually hides many uucp hosts.  For example I have set up
fb.com through uunet, and everything destined for anyone@fb.com is
actually delivered to uucp machine "afbf05" which happens to be a
local call to uunet (D.C. area) but in fact most of the mail is
destined for one of several machines in the Park Ridge IL area connected
by a satellite link.  All of the machines know how to resolve any
variation of user@fb.com (just like a local address, everybody is in
the aliases file), but it would clearly be wrong to change To: user@fb.com
to user@afbf05.uucp when in fact the user isn't there.  Delivery would
not be affected of course, but you will force exactly the problem you
are claiming to be fixing - if someone does a group reply it's going
to bounce through the DC machine just to get back to the local host.

>>If headers aren't munged, you will never see a From: uucpsite!user.  The
>  Maybe that's true from your site, but not from others.

True, but only because there is not a clear standard. Someone has gone
out of their way to break things in the transport just to keep an
already broken user agent happy.  What's worse is that some sites do
prepend their name and others don't, so that form is rarely usable
anyway.  I always use the uucp From_ line for replies which seems
reliable with things that have come through uunet.  Group replies
are more problematic.


>  I sure hope they have changed it by now.  But the last time I tried,
>mail addressed to user%site bounced with host unknown, while mail addressed
>to site!user went though.  The site was not 'chinet', but it was bounced by
>either 'oddjob' or 'gargoyle', which are forwarders for your domain.

I don't doubt it and I suppose you really can't complain about '%' not
working.  But.... If you are doing the munging into user%site@your.domain
it is your host that will be called upon to interpret the reply since
you have guaranteed that it will come back through you.  Thus it doesn't
matter that others don't know how to resolve it (in fact it may be an
advantage).

>Actually, if 'chinet' were a UUCP neighbor, and sent mail for me to
>relay to Internet, I would rewrite 'From: les@chinet.UUCP' as
>one of 'From: chinet!les@mp.cs.niu.edu', or
>'From: les%chinet.UUCP@mp.cs.niu.edu' or 'From: les%chinet@mp.cs.niu.edu'.
>But it would be my choice, not yours.  (I believe I am currently using the
>second of these forms).

What do you expect to happen when the "site!user@domain" form goes back off
the internet down a path to a uucp destination?  Say you get a message
with a destination of fb.com or chinet.chi.il.us from your uucp neighbor. 
In the case of chinet, it will arrive with a couple of other hostnames
prepended to the From: line making a correct interpretation impossible.
In the case of fb.com it will look pretty much the way you write it but
my machines deliberately interpret the !-path first to accomodate a
broken (but not replacable) UA that generates group replies by making
a path back to the sending machine prepended to the To: and CC: addresses.
(But my reply to the sender will work anyway because it will use the
uucp From_ line).

>However, since 'chinet' is not my UUCP neighbor, I rewrite
>'From: les@chinet.UUCP' as 'From: les@chinet.UUCP'.
> The difference is that for my UUCP neighbors I have an obligation of making
>their addresses useable by Internet hosts, and of providing a route back to
>them.  But for a UUCP address which is not a neighbor, I have no such
>obligation to provide a return route.

I would be a little more comfortable if this was worded more like: "I don't
modify les@chinet.UUCP because I have no naming authority for chinet.UUCP."
And this is precisely why I would like to see the uucp <-> internet gateway
machines set up domain names solely for the purpose of mapping their
uucp neighbors into convenient domain style names.  In that case you would
not only have the "authority" to map the names, you would be able to do
it without undocumented or ambiguous kludges.

Les Mikesell
  les@chinet.chi.il.us