Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!agate!ucbvax!decwrl!granite.pa.dec.com!mellon From: mellon@zayante.pa.dec.com (Ted Lemon) Newsgroups: news.newusers.questions Subject: Re: questions Message-ID: Date: 28 Jul 89 03:18:50 GMT References: <4051@udccvax1.acs.udel.EDU> Sender: news@decwrl.dec.com Distribution: usa Organization: Digital Equipment Corporation Lines: 92 In-reply-to: eileen@vax1.acs.udel.EDU's message of 27 Jul 89 21:07:33 GMT Yes, everybody usually has trouble with network addresses when they start. You are on an internet site. That means that you can send mail directly to any other internet site without having to figure out how to get there. Your internet mail address is ``eileen@vax1.acs.udel.edu''. When you see other addresses in a similar form, you should be able to send mail to them. For example, my address is ``mellon@zayante.pa.dec.com''. You can send mail to me just using that address. There are two more kinds of addresses that you need to know about. One of these is somewhat insidious, so we'll examine the easy one first. The easy one is a usenet address. A usenet address consists of a series of host names, starting with one that's a direct connection from yours, and ending with the name of the person you want to get to. For example, if my machine (zayante) had a uucp connection to a machine called gondor, which had a connection to a machine called gnrrf, and I had a friend named bill who had an account on gnrrf, I could send that friend mail using the address ``gondor!gnrrf!bill''. As you can see, there are two sorts of address operators being used here - the ! (bang) and @ (at) operators. The @ operator takes precedence over the ! operator, which means that an address like ``foo!bar@baz'' tells your mailer to send the mail to the machine baz, which will send the mail to the machine foo, which will send the mail to the user bar. It happens that every machine on the internet is next-door to yours, electronically speaking. This means that if you have a friend who is on a machine that's two hops off of the internet from, say, uunet.uu.net, you can send that friend mail using the address ``machine1!machine2!friend@uunet.uu.net'', where machine1 is the machine between your friend's and uunet.uu.net, and machine2 is your friend's machine. There's another operator which acts much like an @ operator, but is used for getting around broken mailers (about which more later). This is the % operator. You can use the % operator to route mail through a known machine on the internet to an unknown machine on the internet, or on a private network. The % operator has a lower precedence than the @ operator or the ! operator (well, I'm completely not sure about the ! operator). This means that mail to foo%bar@baz will go through the machine foo on the way to bar where it will be delivered to the user baz. Now, for the insidious form of address. It's actually a nice form of address, and will make your life much easier once all of the machine on the internet and off it fix their sendmail.cf files, but for now, it does add a bit of confusion. See, at my former job, I was two hops off of the internet. You could send mail to me at ``capmkt!nli!mellon@cogsci.berkeley.edu''. This worked out pretty well, except that it was hard for new news readers to figure out how to get mail to me. Later on, we made an arrangement with uunet whereby we could register a domain address, which looks exactly like an internet address, and through some clever sleight-of-sendmail, I could receive mail from any internet host at the address ``mellon@nli.com''. When an internet mailer goes out to look for nli.com, apple.com (another internet address, run by a very competent postmaster) raises its hand and says ``I know nli.com, I'll take the mail!''. Your mailer then sends the mail to apple.com, who knows how to get mail to me. This has the tremendous advantage that you don't have to know which machines are between yours and mine. All you need is my fully-qualified domain address, and you're home free. The disadvantage comes in in that a lot of internet hosts do not yet support MX forwarding correctly (this is the magic that allows apple.com to accept mail for my old employers). So when you send mail from one of those hosts to ``mellon@nli.com'', it barfs, and you get back a bounce from an evil creature called the Mailer Daemon which says ``nli.com: host unknown''. All is not lost. If you know of an internet host that has a working mailer, you're home free. Just send the mail to mellon%nli.com@good-boy.com, where ``good-boy'' is the name of some host that has a working mailer. I won't post the name of such a host on the net, since doing so would probably result in a deluge of mail forwarded through it. If your machine doesn't have a working mailer (and I have no reason to believe that it doesn't), ask your system manager for the name of a system that does. With any luck, s/he'll be so embarassed that s/he'll actually fix the broken mailer. If not, at least you have a workaround. Good luck! _MelloN_