Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!ginosko!gem.mps.ohio-state.edu!apple!motcsd!hpda!hpcuhb!hpcuha!hp-ptp!toddp
From: toddp@hp-ptp.HP.COM (Todd_Poynor)
Newsgroups: comp.mail.misc
Subject: Re: use of % (was: Making smail2.5 understand <user>%<site>@<site>)
Message-ID: <1960002@hp-ptp.HP.COM>
Date: 17 Oct 89 06:24:56 GMT
References: <126303@sun.Eng.Sun.COM>
Organization: HP Pacific Technology Park - Sunnyvale, Ca.
Lines: 47

>Back to reality now (no hypothetical situations), %-signs should never
>be used without the precense of an @-sign.
  
I'll buy your argument about >mailers< not putting "%" signs on addresses
without @s, but users befuddled by the Internet address syntax may easily
do this.  I see no reason for requiring an @ to be present.
  
>the % is sometimes used but should be treated
>no differently than !'s aside from the fact that %'s are evaluated from
>left to right as opposed to !'s being evalutated right to left.
 ^^^^^^^^^^^^^                                    ^^^^^^^^^^^^^
  
I believe you intended to indicate the opposite directions; at least, this
is what RFC-1123 mandates.  This RFC does >suggest< that "%" have lower
precedence than any other operator, including "!", but does not require it.
However, it's a fairly safe bet that this convention will become rather
widespread, now that it's recommended by such an influential source.
I don't know how prevalent hybrid addresses containing both routing
operators are in the net, but I believe this has usually been discouraged.
  
>Look -- it's like this, plain and simple...
  
Not so plain and not so simple.  This discussion was prompted by your
posting that purported to be a summary of what RFC-1123 said on the
matter, which it decidedly wasn't.  Hence my clarifying posting.
The algorithm you are arguing for is in clear disagreement with section
5.2.16 of that RFC, which fancies itself the new standard for handling
this source routing.  Your algorithm may well be the most commonly-used
today, I don't know.  I do know it is not quite the way the hosts have
been configured where I'm at.
  
So it appears we're running into that time-honored conflict: is the proper
way to do things what the Internet working groups and task forces say to
do, or is it whatever will leave you compatible with the majority of
Internet software out there?  Already there is some discussion in
comp.protocols.tcp-ip on whether these RFCs are being taken seriously by
Internet software vendors ("New Host-Requirement RFCs").  Time will tell.
For the mean time, I'm evaluating bangs before percents, and percents in
right-to-left fashion, and telling users never to mix bangs and percents.
  
The one part I'm holding off on is the use of empty reverse paths ("<>")
in the envelope (section 5.3.3) for failure notification messages.  This
construct loses on the UN*X mailers I've tried it on -- it gets updated
to "<@@hostname>" by the receiving UN*X host.  A message with this envelope
is not long for the world.  Forgive the drift...
  
^todd    "My standard can beat up your standard"