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RE: Possible ambiguity in SMTP RFC2821 - your opinon please

2007-11-26 08:56:41

--On Tuesday, 27 November, 2007 02:13 +1100 Chris Wright
<chris(_at_)ausregistry(_dot_)com(_dot_)au> wrote:


Thank you for taking the time to reply, I have been
experimenting and discovered that even most mail clients wont
accept chris(_at_)au (for example) as a valid email address,
outlook certainly wont, neither will hotmail or yahoo so this
in itself is a problem that would almost be impossible to
tackle. Even if the MTA software did router the mail, it would
be useless with a large majority of email users being unable to
send email to the address (and presumably unable to reply).

Oh well, at least I have my answer.

Once again thanks for replying.

Yes, that MUA problem would be hard to overcome.  We still have
MUAs and web sites that reject addresses in the museum, info,
aero, etc., TLDs, presumably on the grounds that we all know
that TLDs can only be two or three characters long unless they
are "arpa".   That constraint was never built into the DNS
protocols, while the "two or more labels" one is.  Many, perhaps
most of those clients have been fixed in the last half-dozen
years, but the number of bad actors has certainly not reached

So, while 2821bis clearly permits single-component (TLD-only)
domains, my guess is that, to take advantage of it, you will
need to implement it and then start a campaign to disseminate
clues and allow at least a half-dozen years for it to be

Worse, in these suspicious days, I'd expect spam detectors and
the often-lame SMTP implementations on firewalls to treat
messages containing single-component domains in
backward-pointing addresses as suspicious, perhaps suspicious
enough to drop or classify into "junk" folders.  My impression
has been that it is often harder to get such things updated than
to obtain improvements in actual MUAs.  So, even if people could
send mail to you, you might not be able to successfully reach
them with a reply.

In practical terms, it would probably be better to not count on
this working, or at least to provide an alternate address
(chris(_at_)nic(_dot_)au would be traditional) for people to use when their
MUAs balk.

good luck,