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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!ihnp4!mgnetp!we53!busch!wucs!wuphys!plus5!hokey
From: hokey@plus5.UUCP (Hokey)
Newsgroups: net.mail.headers
Subject: Re: From: and To: in UUCP land
Message-ID: <838@plus5.UUCP>
Date: Sat, 17-Aug-85 00:15:34 EDT
Article-I.D.: plus5.838
Posted: Sat Aug 17 00:15:34 1985
Date-Received: Tue, 20-Aug-85 05:44:55 EDT
References: <835@plus5.UUCP> <742@vortex.UUCP>
Reply-To: hokey@plus5.UUCP (Hokey)
Organization: Plus Five Computer Services, St. Louis, MO
Lines: 45

Lauren, I basically agree with you in your point (1) about using @ in the
transport layer if you "know" how the recipient will handle it.  My only
concern is that while it may be OK to send a site an "rmail user@site", I
would not want to send that site a hybrid recipient.

>2) @'s in the To: and From: lines are the ONLY way to maintain
>   822 compatibility with the outside world, and many smaller
>   machines with limited software are starting to act as gateways
>   and can't be expected to do @/! conversion.

I agree with you here, too.  The format of mail in 822 land *outside* of
UUCP land should be in @ format.  *Inside* uucp land it should be in !
format.  Notice that the futzing is done at the gateways, another point
where we agree.

My answer to your point about small machines is to treat them as being
*outside* UUCP land if the machines of which you speak use strict 822
mailers, and treat them as *inside* UUCP land if they only handle ! format.
This means that mail sent to these machines would have the header put (left)
in the correct format by the appropriate gateway (relay) site.

If From: and To: lines are left in @ format, dumb mailers will produce
hybrid routes which will not always parse correctly when the mail gets
to a site which can recognize ! and @.  I like to avoid problems by
making sure they cannot happen.

While we are on the point about >From vs. From: replies, many mailers
will still source-route a From: reply (i.e.: given "From: a!b To: c!d",
a From: reply at c will send mail to a!b and a!c!d.  Very dull.).

A related point which I did not mention, recipients should be specified
in their shortest form; if somebody sends mail to ihnp4!wucs!plus5!hokey,
the To: line should only say plus5!hokey.  (Yes, I know this is a bad
example because plus5 is not syntactically rooted.)  There are nasty
ramifications of multiple recipients while the mail heads off via multiple
sites.  I suspect the solution to this is to always use "short" recipients
and put enough smarts into the mailers to pass stuff along to smarter
neighbors.

Always giving ! precedence over @ in a >From line can produce an erroneous
parse.  I think rpw once showed a very good hypothetical example of this
case, and I believe Peter Honeyman has done likewise.
-- 
Hokey           ..ihnp4!plus5!hokey
		  314-725-9492