🚀 go-pugleaf

In article <5165@elroy.Jpl.Nasa.Gov> Greg Earle asks about such
things as roy%phri@uunet.UU.NET and what connectivity they imply.

Greg, mail has evolved quite a bit since the days of RFC-822, though
there are many old mailers still around.  "%" never implied any
form of connectivity -- it was often used for networks that speak
completely different protocols from SMTP and such.

For example, my address is jbuck@epimass.epi.com.  If you run a
current Internet mailer, it will try to find the host, fail, and then
obtain an MX record telling it to pass the message to uunet.uu.net
(our official Internet forwarder).  If your mailer can't handle MX
records, the equivalent "right thing" will happen if you mail to
jbuck%epimass.epi.com@uunet.uu.net.  The % means "let the host after
the @ deal with the routing".  By the way, you can usually tell if
you have an obsolete Internet mailer if it ever fails with the
message "no such host" for a host outside your own domain (I'm sure
that the mail gurus can come up with exceptions to this statement).
You don't need to know every host, only every top-level domain.  

The UUCP world (at least that subset registered with the UUCP
project) now does routing.  I generally use @, not !, in my mail.

So, neither @ nor % implies any form of link-level connectivity.
Because many UUCP sites attempt to reroute ! paths as well, even
! does not necessarily imply connectivity, though I wish it did.
-- 
- Joe Buck  {uunet,ucbvax,sun,decwrl,<smart-site>}!epimass.epi.com!jbuck
	    Old internet mailers: jbuck%epimass.epi.com@uunet.uu.net

Argue for your limitations and you get to keep them.   -- Richard Bach