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Re: Strict RFC x821 Compliant: MAIL FROM:

2005-07-06 02:42:36

On Tue, Jul 05, 2005 at 06:56:36PM -0400, John C Klensin wrote:
--On Tuesday, 05 July, 2005 13:22 -0400 Hector Santos
<hsantos(_at_)santronics(_dot_)com> wrote:
I understand the legacy issues regarding the trailing spaces,
been there to during the non-interactive to interactive
interfacing design world. But just as there is exception in
2821 (but not in the STD 10),  I think it is practical to
include a reason for why there exist a space tolerance in the
majority of servers on the network.

If 2821bis is about "cleaning", removing ambiguity,
reaffirming consistency, etc, this would be one of them.

I think we disagree.  See above.  2821/ 2821bis are not about
giving in to the lowest competency level commonly encountered
among clients and servers.  To state that again, there is no
reason to permit or require this.  The server implementers who
decide, for market reasons, that they want to support MAIL and
RCPT commands with the space after the colon (or with no pointed
brackets at all, which we have all seen) can do so as a
robustness extension outside the standard.  But let's not
require anyone to do so -- a few strictly-conformant
implementations are probably good for the network.

Being both server coder, and occasional system operator at places
where actual customers try to use their whatever programs to send
email thru, I can tell, that there are levels of 'strictness' that
work, and others that definitely don't work.

Requiring angle brackets in MAIL and RCPT addresses works usually,
but then some odd junk (Windows CE 1.0/2.0 at least) coders hadn't
cared to read the syntax thru properly, and "as long as it works
with sendmail 5.x, it is good" ..  (or some such)

Rejecting messages because "MAIL FROM:" is followed by a space
would reject apparently lots of Outlooks, which form some 60%
of our customers email clients (when counting their x-mailer: headers)
Counting on protocol trace logs...  the rejection would be about
60-70% of all MAIL FROMs in today morning traffic.

Trailing spaces don't happen at all (except in some QUITs, which
is rather strange in itself..)

Even more sloppy processing is needed, because some customer programs
just don't bother with giving any HELO/EHLO greeting at all.
Of those that give it...  some 99% give completely rubbish text
(whatever user has decided to call the machine - or just some random
that the machine calls itself with: "FamilySmith" -style is common)
Some greet with their or server's IP address in brackets, or more
commonly, without brackets, etc.    Some machines are clearly behind
some NAT box:  "EHLO []"  (yup, it had correct brackets)

If somebody greets with correct name matching remote IP reversal,
that one is a rarity indeed among these consumer customers.

If something under 1% would be affected by strict rules, such
rules could be enforced.  Now it is impossible.

At an inbound server the statistics are different, but I won't
analyze them now.


/Matti Aarnio   <mea(_at_)nic(_dot_)funet(_dot_)fi>
FUNET:  Finnish Academic and Research Network
        Network Information/Software Archival Service