dce@Solbourne.COM (David Elliott) (05/08/89)
We use uucp, and when we get mail from the outside world, it is
often the case that the From: line doesn't match the Return-Path:
line. For example, I received a message this morning in which
the lines were:
Return-Path: <nbires!usenix!uunet!apple.com!timo>
From: Timo <usenix!uunet!apple.com!timo>
This same thing happens if one of the sites involved is "pyramid",
and at one time also happened with "verdix".
I talked to the folks at pyramid last year, and was told that
it is actually improper for mailers to modify the From: line.
I need to explain to people in my company why they need to be
careful when replying to mail messages from outside.
--
David Elliott dce@Solbourne.COM
...!{boulder,nbires,sun}!stan!dcebrian@ucsd.EDU (Brian Kantor) (05/09/89)
The question of why a From: and a From_ line might differ on received mail comes up about annually; I guess it's about time again. In a pure RFC822 compliant world, it would never be necessary to update the From: line when mail passed through your site. If the from address reaching you ALWAYS looks like user@host.dom.ain then you are living in the right world and don't have to worry about this. This is because such addresses can be considered to be "absolute" - they are complete in themselves and do not need any references to be used. UUCP bangist addresses, on the other hand, are NOT "absolute", they are relative. A uucp "address" of the form sitea!user is not a complete address, but rather is a path, either complete or incomplete. When such a path is found on a from line in a message entering your machine, it is valid only insofar as it is relative to your machine, which means that you must update it if you relay the message onward. If you pass the message on via uucp, you MUST prepend your uucp sitename! to the front of the path. If you relay it onto an RFC822- compliant network, you must indicate that relative addressing from your site by appending the '@host.dom.ain' of your relay machine to the address. Thus the answer that you received from Pyramid that "one must never alter a From: line" is incorrect and reflects an incomplete understanding of the current multi-network mail world. You do NOT update a From: line if it is a valid RFC822-style address, but if it is a bangist-only line, you MUST prepend yourhostname! to the front of it. Note that a!b!c!u@e.f.g IS a valid RFC822-style address, and you would correctly LEAVE IT ALONE if you received it in a from line, since it is already an "absolute" address. Summary: u@host.dom.ain - don't touch a!b!u@host.dom.ain - don't touch a!b!u - prepend us! - or - - append @us.dom.ain BTW, some sites currently passing mail are using the original mongo-stupid Unix mailer that doesn't even know what a From: line IS, much less how to update it. Mail passing through these sites is fated to be terminally mangled and probably can't be replied to. All you can really do about this is warn your users and avoid those sites. Brian Kantor UCSD Postmaster UCSD Office of Academic Computing (619) 534-6865 UCSD C-010, La Jolla, CA 92093 USA fax: 619 534 7018 brian@ucsd.edu BRIAN@UCSD ucsd!brian
jbuck@epimass.EPI.COM (Joe Buck) (05/10/89)
In article <1697@ucsd.EDU> brian@ucsd.edu (Brian Kantor) writes: >BTW, some sites currently passing mail are using the original >mongo-stupid Unix mailer that doesn't even know what a From: line IS, >much less how to update it. Mail passing through these sites is >fated to be terminally mangled and probably can't be replied to. All >you can really do about this is warn your users and avoid those sites. On the contrary. Such mailers are correct, it is Berkeley who screwed the world by putting bang paths in the From: header! A mailer that doesn't know what a From: header is has the virtue that it never messes one up. The only mailers harmed by dumb UUCP mailers not updating From: lines are those that attempt, INCORRECTLY, to use the From: line as a relative bang path. Dumb UUCP mailers, UUCP sites running smail, RFC976-compliant UUCP-Internet gateways, and Internet sites can all get along beautifully. Note that none of these guys alter a From: header if one is already present. In this perfect world, someone with a plain-vanilla UUCP mailer would mail to foo!bar!biff!uunet!bilbo.bigschool.edu!user and not include a From: header at all. As long as mail passes through vanilla UUCP sites, no From: header is generated. When it is necessary to generate a From: line (at the gateway, or at the first registered domain site), we make one: From: foo!bar!sender@localsite.domain Yes, it's mixed, but since only RFC-822-compliant sites read From: lines there is no possible ambiguity: the "@" takes priority. Going in the other direction (from Internet to UUCP-land) there is also no need to rewrite the From: line. We must generate a From_ line, but thanks to RFC976 that is easy: From bilbo.bigschool.edu!user Mon May 8 16:02:45 1989 remote from gateway Unfortunately, it is too late to save the world. Berkeley has already wrecked things by releasing sendmail to the world and encouraging every site admin with too much time on his or her hands to hack away at it, and the original sendmail had no way of doing the correct thing to both the From_ line and the From: line at the same time. Given the world we're in, Brian (in the part of the article I didn't quote) is right: if you get a From: header with no @ in it, you'll need to rewrite it. But it is the mailers that generate such things that are in error, not the vanilla V7 Unix mailers, which can be made to interoperate with the rest of the world quite nicely. -- -- Joe Buck jbuck@epimass.epi.com, uunet!epimass.epi.com!jbuck
si1@rosemary.cs.reading.ac.uk (Simona Ingignoli) (05/24/89)
Hello, this is my second attempt to get on the net. I hope it succeeds. Does anybody know how to get to the top level of rn? Bye