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From: dpk@brl-sem.UUCP
Newsgroups: comp.mail.headers
Subject: Re: Routing using @host1:@host2:user@host3
Message-ID: <608@brl-sem.ARPA>
Date: Tue, 3-Feb-87 03:07:42 EST
Article-I.D.: brl-sem.608
Posted: Tue Feb  3 03:07:42 1987
Date-Received: Wed, 4-Feb-87 00:42:56 EST
References: <4611@mit-eddie.MIT.EDU> <837@astrovax.UUCP> <1322@ncr-sd.UUCP>
Reply-To: dpk@brl.arpa (Doug Kingston)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 62
Keywords: routed addresses RFC-822
Summary: Its not valid.  Use "phrase <@H1,@H2,@H3:U@H4>"

In article <1322@ncr-sd.UUCP> matt@ncr-sd.UUCP (Matt Costello) writes:
>What is the status of using
>	@host1:@host2:user@host3	# 1
>versus the 'correct' but ugly
>	@host1,@host2:user@host3	# 2
>
Only the second form (#2) is correct and only if the address above
is preceded by a phrase and enclosed in angle brackets.  See RFC-822 for
details and read the grammer.  It's quite explicit.  In an SMTP transaction
the phrase and angles can be dropped as the address is enclosed in angles
already.  To quote the standard (page 27 of RFC-822):

     Standard for ARPA Internet Text Messages

     6.  ADDRESS SPECIFICATION

     6.1.  SYNTAX

     address     =  mailbox                      ; one addressee
                 /  group                        ; named list

     group       =  phrase ":" [#mailbox] ";"

     mailbox     =  addr-spec                    ; simple address
                 /  phrase route-addr            ; name & addr-spec

     route-addr  =  "<" [route] addr-spec ">"

     route       =  1#("@" domain) ":"           ; path-relative
=====================^ Indicates a comma separated list (see section 2.7)

     addr-spec   =  local-part "@" domain        ; global address

     local-part  =  word *("." word)             ; uninterpreted
                                                 ; case-preserved

     domain      =  sub-domain *("." sub-domain)

     sub-domain  =  domain-ref / domain-literal

     domain-ref  =  atom                         ; symbolic reference


>Do InterNet routers correctly handle the colon form of the address?
No.

>I've noticed that sendmail sites tend to use form #1, and MMDF sites
>(on CSNET) tend to use form #2.  What I'd really like to know is if
>form #1 is enough of an unofficial standard (like the magic '%' rule)
>to make it universally acceptable?
No.  Don't use it.  If SENDMAIL is then its wrong and should be fixed.

>Matt Costello, matt.costello@SanDiego.NCR.COM (registered w/ CSNET)
>	{sdcsvax,cbatt,dcdwest,nosc.ARPA,ihnp4}!ncr-sd!matt

I am certainly not going to defend it as being the most elegant standard
that could have been chosen, but its the one we have and it must be
conformed with as it exists.


	-Doug-
Ballistics Research Laboratory, <dpk@brl.arpa>