Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wasatch!cs.utexas.edu!uunet!mcvax!ukc!kl-cs!jonathan
From: jonathan@cs.keele.ac.uk (Jonathan Knight)
Newsgroups: comp.mail.misc
Subject: Re: sigh (was Re: Short-circuiting a route)
Message-ID: <656@kl-cs.UUCP>
Date: 6 Jul 89 21:59:28 GMT
References: <1888@prune.bbn.com>
Organization: University of Keele, England
Lines: 67

From article <1888@prune.bbn.com>, by rsalz@bbn.com (Rich Salz):

> (BTW, does it really use a % hack?  Ick...)
> 
>         The Moral:  don't put full domain names into email paths if
> they're going through the Internet and you don't want them short-circuited.
> Hack the path to be something like
> 	noe!packet_radio!kg6kf_ampr_org!callsign!callsign

Are you serious?!?  Good grief this is worse than the % hack you mocked
earlier.

As I understand it, the argument for re-routing and short-circuiting
revolves around the idea that some people feel they know how
to route mail better than the people who started the mail off.

I thought that the purpose of FQDN's was to get around this
problem.  So everyone should send their mail to a@b and let
the mail software deal with it.

The mail software should decide how to get to the next machine and
deliver it to the destination or re-write the rule as a%b@d to use 'd'
as a mail forwarder.  'd' could do whatever it liked with it as the
mail was now SEP (someone elses problem).

Sometimes, the mail must go through 2 forwarders.  I have a few examples
on this machine, one for CSNET.  So if someone sends mail to
superman@whatever.csnet then my mailer duly decides that the forwarder
for that machine is "relay.cs.net".  Unfortunately I can't get to that
machine and so the mailer has to re-process the address 'relay.cs.net'
to find another forwarder.  In this case it is 'nsf.ac.uk'.  So
the route becomes "superman%whatever.csnet%relay.cs.net@nsf.ac.uk"
and the mail then leaves here.  (actually it would be in GreyBook
order to obey the protocol in force here, but I didn't want to
confuse anyone so I put it in the order that USA people can easily
follow)

It is possible that I could have pointed all my .csnet mail to nsf
for forwarding, it may know about the .csnet domain.  But that is
wrong because nsf does not advertise itself as a csnet forwarder,
relay.cs.net does that.   So my route is correct because I forward
mail for the .net domain to a .net forwarder.  I then direct
mail for the .csnet domain to a .csnet forwarder.

If a short-circuiter got hold of the above it may try and send
the mail to 'whatever.csnet' which may fail (depending on how
the mailer is configured).  But what's the point of short-circuiting
the route when it is probably going to work perfectly well as it is.
If it doesn't then the sys admin at the site which originated it
is going to get a bounced mail message which will encourage him or
her to fix the problem.

I could never understand why people insist on re-routers and short
circuiters which are aimed at solving a problem which should not
exist and would not exist if mailers bounced mail with an error
message every time it goes wrong.

Re-routing is very impolite, if I want my mail routed then I won't
put a route on it, but if I do put a route on it then I'd be
grateful if people would use it.  If the sys admins think that they
can route mail better than I can, then declare yourselves as forwarders
for those domains and I will gladly dump my mail on you for you to route.
-- 
  ______    JANET :jonathan@uk.ac.keele.cs     Jonathan Knight,
    /       BITNET:jonathan%cs.kl.ac.uk@ukacrl Department of Computer Science
   / _   __ other :jonathan@cs.keele.ac.uk     University of Keele, Keele,
(_/ (_) / / UUCP  :...!ukc!kl-cs!jonathan      Staffordshire.  ST5 5BG.  U.K.