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From: steve@dartvax.UUCP
Newsgroups: net.mail.headers
Subject: Re: internetwork addressing questions, with sendmail.cf fix
Message-ID: <2214@dartvax.UUCP>
Date: Wed, 18-Jul-84 22:56:01 EDT
Article-I.D.: dartvax.2214
Posted: Wed Jul 18 22:56:01 1984
Date-Received: Sun, 22-Jul-84 03:06:03 EDT
References: <694@hou3c.UUCP> <1547@sun.uucp>
Organization: Dartmouth College
Lines: 53

>To answer just a few of the questions:
>	2) Since '%' (percent) it isn't part of the RFC822 grammer, what 
>	does it mean and what is the convention for parsing it?  
>It is a kludge invented somewhere on the Arpanet which was used to get
>around the rule that "there can only be one '@' in an address".  If you
>send something to user%host@gateway, by 822 rules it should go to 'gateway'.
>There at the gateway, the 'user%host' part is subject to local rules, and
>it turns out that treating it as 'user@host' is a very useful local rule,
>given the current chaotic state of the various interconnected nets.
	...

>This is the section of our sendmail.cf (at the end of ruleset 3) which
>implements the non-precedence.  The important part is that the leftmost
>token to match be '$-' rather than '$+'.  Note that this also parses
>the new uucp transport-addrs (host.domain!user).  Enjoy.
>
># convert old-style addresses to domain-based addresses
># All old-style addresses parse from left to right, without precedence.
># Note that the left side of '%' is a username; it is matched with $+ so
># that complex names like "john.gilmore%l5" will be caught and translated.
># The rest can only have an atom as the host name (left of the symbol).
>R$-:$+			$@$>3$2@$1			host:user
>R$-^$+			$1!$2				convert ^ to !
>R$-!$+			$@$>6$2<@$1.uucp>		uucphost!user
>R$-=$+			$@$>6$2<@$1.bitnet>		bitnethost=user
>R$-.$+!$+		$@$>6$3<@$1.$2>			host.domain!user
>R$+%$+			$@$>3$1@$2			user%host

The only catch is that if "%" is really a "@" in hiding, then it should
be parsed right-to-left, not left-to-right like the other forms.  In
particular, if you are parsing  user%hostA%hostB, you want it to become
user%hostA@hostB, not user@hostA%hostB.  An alternative section of
sendmail.cf would be:

# convert old-style addresses to a domain-based address
R$+^$+			$1!$2				convert ^ to !
R$-!$+			$@$2<@$1.uucp>			resolve uucp names
R$-.$+!$+		$@$>6$3<@$1.$2>			host.domain!local-part
R$+%$-			$@$>6$1<@$2>			local-part%host
R$+%$-.$-		$@$>6$1<@$2.$3>			local-part%host.domain
R$-:$+			$@$>6$2<@$1>			host:local-part
R$-=$+			$@$2<@$1.bitnet>		resolve bitnet names

One limitation with this is that it fails to parse  

	local-part%host.subdomain.domain

correctly.  Comments?
--------------------------------------------------------------------
Steve Campbell

	UUCP: {decvax|linus|cornell|astrovax}!dartvax!steve
	CSNET: steve@dartmouth     ARPA: steve%dartmouth@csnet-relay