Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!cmcl2!yale!husc6!think!nike!ucbcad!ucbvax!hplabs!hpcea!hpfcdc!hpfclp!diamant From: diamant@hpfclp.HP.COM (John Diamant) Newsgroups: net.mail Subject: Re: Do you rewrite "From:" lines? Message-ID: <4260001@hpfclp.HP.COM> Date: Sat, 4-Oct-86 17:41:26 EDT Article-I.D.: hpfclp.4260001 Posted: Sat Oct 4 17:41:26 1986 Date-Received: Tue, 7-Oct-86 19:45:03 EDT References: <736@ncc.UUCP> Organization: H-P Fort Collins Lines: 85 In article <358@tc-jeff.fluke.UUCP>, jeff@fluke.UUCP (Jeff Stearns) writes: > Now that I've installed smail, a nasty question comes up. Should our sendmail > modify "From:" lines? > > Background: > We're a uucp site with a dozen or so neighbors. We're running Berkeley > UNIX with sendmail. We just installed smail. > > Our standard sendmail rewrites "From" and "From:" lines. Specifically, > it prepends our sitename to the address. This is standard practice here > in uucp-land. All of our uucp neighbors do it, too. > > The problem: > I've just installed smail. We're getting domain-ized. We're trying to > make a separation between domain addresses and uucp routes. > > What to do with the "From:" line? > > I believe that the theoretically correct answer is this: > Don't touch the "From:" line at all. Do your playing with the > "From" line, so that "From" can indicate a valid UUCP path, > leaving the sender's domain address in "From:". > (That last part is a quote from the smail manual page.) > > And this is what smail does. > > But all of our neighbors tack their sitename onto the "From:" line as well! > There's gonna be lots of unreplyable(?) mail if we start playing by The Right > Rules while everybody else is Doing What The Majority Does. (Recall that > 4.2BSD /usr/ucb/mail sends replies to the "From:" address, not the "From" > address.) > > What's a mother to do? > -- > Jeff Stearns (206) 356-5064 > John Fluke Mfg. Co. > P.O. Box C9090 Everett WA 98043 > {uw-beaver,decvax!microsof,ucbvax!lbl-csam,allegra,ssc-vax}!fluke!jeff Smail is telling you exactly the right thing to do. 4.2BSD Mail does the right thing by using the From: lines since it has sendmail available to it, it is expected to be able to handle 822 style addresses. If it reads an 822 header ("From:") and doesn't understand such a header, it is just plain wrong! SYS V mailers, on the other hand, look at "From " lines, because they don't understand 822 style addresses. "From:" lines will only be generated by sites that understand 822 (or they are wrong). Given that this is the case, if a "From:" line exists, you should assume it is correct. The only time you have to do something funny is if you get are gatewaying a piece of mail from a non-822 site, you will have to add a "From:" line since it doesn't already have one. Here is an example: say your neighbor runs standard SYS V (non-822) and is called "dumbsite", and you are called "gateway.com", and that the user called "user" is sending a message through you. You cannot generate a From: line of user@dumbsite because nobody understands that except dumbsites neighbors. You have a choice of: user%dumbsite@gateway.com or dumbsite!user@getway.com. I have discussed this with Mark Horton (by mail) and he claimed that the second address is O.K. because anyone looking at the From: line must have "@" precedence. While he is technically correct, this is very dangerous, because as you say, there are many sites out there that don't follow rules. The first one should work fine, as long as you make sure your site can translate the address back into UUCP style before transmitting it. You are correct about it being a large problem that people are modifying the From: lines. However, anybody who succeeds in replying to such mail also must have a broken mailer. An "@" is required in a From: line and must take precedence over any other address token (like "!"). So, in fact, tacking on a "!" at the beginning is wrong and is unreplyable by a mailer that conforms to standards. The only thing I can suggest is that the more people who conform to standards, the more likely everyone else will be to conform (because it will hurt them not too). As far as how many people already conform, consider that the entire ARPA Internet does, which means all those From: lines are already not replyable via gateways into the Internet. I encourage you to not modify From: lines and convince your neighbors not to also. The faster we get people to start doing the right thing, the smaller the problem will be -- the real problem is getting a critical mass of people to conform. John Diamant Systems Software Operation UUCP: {hplabs,hpfcla}!hpfclp!diamant Hewlett Packard Co. ARPA/CSNET: diamant%hpfclp@hplabs.HP.COM Fort Collins, CO