Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!uunet!intercon!amanda@mermaid.intercon.com From: amanda@mermaid.intercon.com (Amanda Walker) Newsgroups: comp.protocols.tcp-ip Subject: Re: MXing the world (was RE: New Host-Requirement RFCs) Message-ID: <1523@intercon.com> Date: 30 Oct 89 23:45:33 GMT References: <8910201839.AA29376@arcturus.mitre.org> <1136@odin.SGI.COM> <1156@odin.SGI.COM> <71081@uunet.UU.NET> <299@dranet.dra.com> Sender: news@intercon.com Reply-To: amanda@mermaid.intercon.com (Amanda Walker) Organization: InterCon Systems Corporation Lines: 37 In article <299@dranet.dra.com>, sean@dranet.dra.com (Sean Donelan) writes: > 3. The "what do you care?" point. The %-hack is in the local part anyway. > It should only be the concern of the sender and the gateway. If you're not > a gateway don't worry, if you are a gateway its your job to worry. This is fine when there is only one gateway involved. What happens when I need to go through a number of gateways, each of which has its own magic local part? One of the big problems with mixing addresses and routes (which is what using % does) is that it can give you some real ambiguity headaches. Consider the "address" random!mumble%foo!bar%zot@foobar.domain from a UUCP site whose mailer understands both RFC 822 addresses and UUCP routes (as many do these days). How do you send mail to this person? Answer: you pray, and your mail probably bounces somewhere, not because any individual pair of hosts don't talk to each other, but because you can't tell them where you want the mail to go unambiguously. This is something that the DNS and MX records are very good at addressing, as Karl has pointed out with his CompuServe example. Anyone who thinks my example is contrivedly complex is either new to inter- network mail or doesn't try to send mail to certain organizations that shall remain nameless for the moment (which use DECnet and VMS mail :-)). Also, any time a gateway cobbles up a source route in the local part, you run the (very real) risk of ending up with one-way mail. A good friend of mine is currently on a site that can send me mail, and to which I can send mail. However, in both directions the return address gets mangled beyond usability, thanks to helpful bangs and %s in the local part. As it happens, using simple domain addresses works great (thanks to the DNS and pathalias), but the gateway doesn't know this :-(... I've also gotten plenty of mail replying to articles I've posted in which the return addresses are undecipherable, thanks to gateways using source routing. -- Amanda Walker