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Re: Question on how bang-paths worked from the old days

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On Monday, August 2, 2021 at 3:23:23 PM UTC-5, John Levine wrote:
> It appears that John Goerzen <jgoe...@complete.org> said: 
> 
> Later on we had the uucp mapping project so you'd send mail to c!bob and your mail server would 
> look up c in the map, prepend the path, and send it on its way.

Interesting.  sendmail would call pathalias or something, I guess?  I had heard of the maps but hadn't heard of this kind of integration!

> >2) Was there any sane "reply" function in mail software, and if so, how would it compute a reply path?
> Once we had the maps, yes, before that, not without hand editing the address.

Cool.  That makes sense.

> >sending a message to host1!host2!host3!user, it would run 
> > 
> >uux ... host1!rmail host2!host3!user 
> > 
> >(I think?) Is that correct?
> Yes.
> >So why would it not have done: 
> > 
> >uux .... host1!host2!host3!rmail user 
> > 
> >instead, using UUCP routing to get all the way to the destination? Perhaps these added From lines have part of the answer (being needed to compute a Return-Path?)
> UUCP routing? There was and is no such thing. The uux command only knows how to send 
> a command and an input file one hop. 

Wow.  That is a detail I had totally missed.  I guess it does make sense given what I remember of the UUCP queue format; the destination node was encoded only in the directory name (at least in Taylor), IIRC.

> That's why we needed the mapping project to put source routes in the rmail commands.

That totally makes sense now, thank you.

> >And, an any case, what program along the way was adding the extra From or >From lines?
> The Unix mail program prepended the From line when it stored the 
> message in the recipient mailbox. (Still does, in fact.) It is the 
> delimiter between messages. 
> 
> If that sounds like a really lame idea that someone might have 
> invented in two seconds in the 1970s, yup. 

There's something deeper going on here than just the mbox format.  So if you're host2 in a host1!host2!host3!user message, you're not going to be writing the message into any kind of mailbox - you'll be passing it on to rmail host3!user.  From what I can gather, it was expected that every hop along the way would add a "From " or ">From " line identifying itself.  Even today, the rmail packaged with sendmail collapses these into a bang path that is basically the return path, and uses them as the -f parameter to the sendmail invocation when it eventually pipes the message on to sendmail.  I found an oblique reference to this as the "UUCP From_ header lines" in an early version of a sendmail book.  The strong implication I am getting is that rmail/MTA in some fashion was adding just just a Received: header but also a "From_" header at each hop, and the From_ headers (NOT the RFC822 From: line) were processed and coalesced by rmail to form the envelope from (same as SMTP MAIL FROM:).

That much I can deduce by reading the source code to rmail (which, though not terribly long, is terribly old C and not the easiest read).  What I haven't figured out is what the mechanism for adding those extra From_ headers was.  Was it delivermail (sendmail predecessor) doing it?  Or surely something in the Sendmail configuration may have been?  I grabbed the earliest sendmail I could easily find (from 2000) but it didn't have easy answers to this question either.

> By the way, FreeBSD and probably other unix-ish systems still come with uucp and uux. 
> If you want to experiment, you can try them out. 

Oh yes, I've got a couple UUCP nodes running Debian on Docker.  I used UUCP "back in the day", but not far enough back in the day for this.  In the 90s, I lived in a rural area and used UUCP on FreeBSD and then Debian as a way to get email.  Later I worked for the ISP that had provided me the UUCP feed, and was (by then) the guy designated to administer our by then barely-used UUCP service, which ran on BSD/i.  As far as I can recall, all of these were Taylor UUCP.  They were all used for email and Usenet, but solely for leaf sites hanging off the Internet, so domain addressing was used everywhere, file copying wasn't used at all, and uux was used only as a means to invoke rmail and rnews.  So it was a pretty limited view of UUCP, and I didn't really understand the breadth of what had been UUCPNET until a number of years later when things like Usenet archives and search engines became more widely available.

So while I'm familiar with UUCP itself, UUCPNET (as more than a node that dials into exactly one place (an ISP) because of lack of dedicated link) was just before my time.

I did participate in other store-and-forward networks in the 90s, from the BBS world: primarily FidoNet and VirtualNet.

Thanks John!

- John

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Question on how bang-paths worked from the old days John Goerzen <jgoerzen@complete.org> - 2021-08-01 20:52 -0700
  Re: Question on how bang-paths worked from the old days John Levine <johnl@taugh.com> - 2021-08-02 20:23 +0000
    Re: Question on how bang-paths worked from the old days John Goerzen <jgoerzen@complete.org> - 2021-08-02 14:11 -0700
      Re: Question on how bang-paths worked from the old days Grant Taylor <gtaylor@tnetconsulting.net> - 2021-08-02 17:44 -0600
    Re: Question on how bang-paths worked from the old days Grant Taylor <gtaylor@tnetconsulting.net> - 2021-08-02 17:24 -0600
      Re: Question on how bang-paths worked from the old days John Levine <johnl@taugh.com> - 2021-08-03 02:24 +0000
        Re: Question on how bang-paths worked from the old days Grant Taylor <gtaylor@tnetconsulting.net> - 2021-08-02 22:35 -0600
          Re: Question on how bang-paths worked from the old days Crypto God <CryptoGod@china.com> - 2021-10-09 05:00 +0000
            Re: Question on how bang-paths worked from the old days Avon Kerr <avon@bbs.nz.invalid> - 2021-10-13 22:02 +1300
            Re: Question on how bang-paths worked from the old days <joe@example.invalid> - 2022-02-27 10:48 +0000

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