🚀 go-pugleaf

> >Nonsense.  I have much better info than that.  My mailer extracts the
> >paths from all incoming mail and puts it (with a timestamp) into the
> >database.  I thus have good info on good paths to those people who
> >have sent me mail lately.  This is at worst the same data as is used
> >by the mailers; it is usually better.
> 
> Er, no.  It is never wise to assume that a mail path works both ways.
> An example I saw recently: someone was sending mail from Tektronix to
> MIT using the path fragment ..!allegra!eddie!athena!user.  It was their
> dumb luck that allegra realized that "eddie" was the same machine as
> mit-eddie (aka eddie.mit.edu), AND that eddie  would resolve "athena" as
> athena.mit.edu (which is mit-athena in the uucp world).
> 
Er, I hear what you're saying, but my experience is otherwise.  It's
true that some links don't work in both directions equally well.  From 
here, I can get mail to my neighbors within minutes; they must wait for 
my call to deliver mail here.  This is fairly common, but it doesn't
interfere with reversing a path.

Some links are truly one-directional.  In such cases, a path-reversal
simply won't work, unless there's an intelligent forwarder on this
side of the bad link.  

The above example falls into this class, but in a truly original way.
In effect, the link has been made one-way by having one of the machines
lie about its name in the path.  This is truly perverse!  

Despite the efforts of programmers and administrators to make life
difficult, the fact is that in the current email network, path reversal
is still the most effective way to respond.  I have three neighbors
with fairly intelligent forwarders, and when I submit mail with only
"To: target!user" or "To: user@target", the chance of it being delivered
is around 40%.  When I send it through the same hosts with a reversed
path, the success rate is around 90%.  It would be better, but a fair
number of the full paths are subverted and redirected along bogus paths
by some "intelligent" forwarder along the path.  Thus, all four of my
neighbors talk to harvard; if the reverse path goes there, their mailer
rewrites it, and is wrong about as often as it is right.

If all mailers were willing to accept pure bang paths and not question
them, I claim that path reversal would succeed in well over 99% of the
cases.  

It's true that a reversed path will fail some percentage of the time.
But replacing a method that fails 1% of the time with one that fails
60% of the time (at this site) doesn't seem to me to be much of a win.

-- 
John Chambers <{adelie,ima,maynard,mit-eddie}!minya!{jc,root}> (617/484-6393)