🚀 go-pugleaf

[me:]
   >[b] Rabid rerouter against UUCP road kill: If you would not try to use
   >Internet FQDN host addressing in !-paths, or at least leave things out
   >of the Internet once they've left it, you wouldn't have to worry about
   >mail loops...and it WORKED before you mucked with such dangerous,
   >unpredictable options at intermediate sites you don't control.

chip@ateng.com writes:
   Argument [b] doesn't hold up.  Fully Qualified Domain Name host addressing
   is not only for Internet hosts; rather, it is the standard way of naming
   hosts reachable from the Internet.  Consider all the domains without
   Internet connections -- much of EUNet, for example, or Ateng.COM. :-)

On the contrary...

If a piece of mail arrives here specifying an envelope
	some!where!over!the!rainbow!ateng.com!chip
my sendmail configuration will slice, dice, and julienne-fry it into
	chip@ateng.com
whereupon sendmail will look up ateng.com, find that the MX is
uunet.uu.net, and send it there...just one hop from you, where you
routinely expect high-quality, reliable mail transfer service.

The fact that you're not on the Internet is irrelevant; assuming that
an MX host is "close" to the intended destination (fidonet.org does
not currently apply, but I'm working on that), I strip out a lot of
intervening, unreliable cruft in order to reach that destination.

I tend to think of this as better mail relay service, not an abuse of
paths.  I've never yet had anyone complain to me about it.

   Must all bang paths be beheaded when they reach the Internet, just because
   _some_ of their brethren are invalid?

Probably.  Their success rate is comparatively low, especially when
the path is "long."  Too many sites still have news interfaces
replying to Path: headers.  The success rate of MX'd FQDN destinations
is a _great_ deal higher.

--Karl