Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!princeton!astrovax!wls
From: wls@astrovax.UUCP (William L. Sebok)
Newsgroups: comp.mail.headers,comp.mail.uucp
Subject: Re: more about autorouting
Message-ID: <837@astrovax.UUCP>
Date: Fri, 23-Jan-87 14:05:25 EST
Article-I.D.: astrovax.837
Posted: Fri Jan 23 14:05:25 1987
Date-Received: Sat, 24-Jan-87 05:38:07 EST
References: <14396@amdcad.UUCP> <4611@mit-eddie.MIT.EDU>
Reply-To: wls@astrovax.UUCP (William L. Sebok)
Organization: Princeton Univ. Astrophysics
Lines: 47
Xref: mnetor comp.mail.headers:100 comp.mail.uucp:170

>This seems unnecsary to me, since RFC822 compliant address can still
>specify routing.  The syntax for this is @host1:@host2:user@host3.
>I've been told that the ":"'s should be ","'s except for the
>right-most one (as the Berkeley sendmail configuration does), but I've
>been unable to find this stated in RFC822 (could someone send me a
>reference, if the ","'s are actually correct).

I have had severe problems writing a sendmail.cf that would properly handle
addresses of that form:

@host1,@host2,@host3:user@host4

The basic problem is that the sendmail parser wants to take the above address
and break it apart at the commas.  This effect can be turned off if the address
is enclosed in angle brackets.  However 1) what if the user forgets to use
angle brackets? and 2) what if your mailer receives from another site an
address of that form that is not enclosed in angle brackets?

Here is one place I ran up against a wall when I did my recent complete rewrite
of our sendmail.cf script.  When gatewaying from uucp to sites reachable by
SMTP I want to avoid creating From: and envelope From addresses that mix !'s
and @'s (I treat "From:" and "envelope From" together here because, as
previously discussed, an unhacked sendmail does not provide the ability to
treat them differently).  I handled !'s in addresses by dividing the SMTP
reachable world into two classes.  Those sites that understand !'s in an
address are sent the address untouched.  For the strict RFC822 sites, those
that don't understand !'s in an address, the string of ! connected sitenames is
turned into an RFC822 route. This is in the theory that when the reply to that
message reaches here that my site can turn it back it to a ! format route and
that, as is likely to be true, the site sending the reply does not otherwise
know how to get mail back to the original sender of the note.  When a ! route
is turned into RFC822 route it needs to be surrounded by angle brackets to
protect it from sendmail's parsing.  However,  the ruleset trying to do this
has no idea whether the original address was surrounded by angle brackets
(sendmail passes what is inside them to the ruleset and the replaces what was
inside with the output of the ruleset). The safest thing to do seemed to be to
have the ruleset put a set of angle brackets around it. But then, if they were
already there, then two sets of angle brackets would be around the address.  I
am not sure if <<address>> is legal RFC822.  I do know that some sites reject
it.

I don't know why the framers of RFC822 chose that form of syntax.  The form
@host1:@host2:@host3:user@host4 would really have been much easier to parse.
-- 
Bill Sebok			Princeton University, Astrophysics
{allegra,akgua,cbosgd,decvax,ihnp4,noao,philabs,princeton,topaz}!astrovax!wls
one of these days:	wls@astrovax.princeton.edu