Xref: utzoo comp.mail.misc:772 comp.mail.uucp:917 Path: utzoo!mnetor!uunet!epiwrl!epimass!jbuck From: jbuck@epimass.EPI.COM (Joe Buck) Newsgroups: comp.mail.misc,comp.mail.uucp Subject: Re: Do `%' and `!' imply (Data link layer) connectivity information? Message-ID: <1804@epimass.EPI.COM> Date: 6 Jan 88 18:52:24 GMT References: <5165@elroy.Jpl.Nasa.Gov> Reply-To: jbuck@epimass.EPI.COM (Joe Buck) Organization: Entropic Processing, Inc., Cupertino, CA Lines: 31 Summary: No connectivity is implied 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,}!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