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Re: Dotless domains

2009-01-24 20:48:55

In message 
<20090125001418(_dot_)76555(_dot_)qmail(_at_)simone(_dot_)iecc(_dot_)com>, John 
Levine writes:

A friend* wonders about the SMTP treatment of addresses in TLDs.
Historically there have been a smattering of such addresses, most
famously n(_at_)ai, and there are 21 TLDs with MX records, but spot
checking shows that most appear to be config mistakes, with the MTAs
not actually accepting mail to postmaster(_at_)tld(_dot_)

If ICANN does what they claim they're going to do and starts selling
thousands of new TLDs, we're likely to see a lot more dotless
addresses.  bob(_at_)aol, anyone?

As best I understand it, the prose description of addresses in 2821
allowed TLDs in addresses, but the ABNF didn't.  In 5321 the ABNF
changed to match the prose.  Although the DNS allows you to put a dot
at the end of a domain name to make it clear that it's an absolute
address, SMTP has never allowed that.

My impression is that in the real world, mail addressed to
postmaster(_at_)va is far more likely to be rewritten to
postmaster(_at_)va(_dot_)example(_dot_)com than delivered to the Vatican 
(which, as it
happens, will accept it.)  Mail addressed to postmater(_at_)va(_dot_) with a 
isn't valid under 821, 2821, or 5321, so some MTAs accept it, some
reject it.

Is the current situation with TLDs deliberate, or was the change in
5321 just aesthetic tidying up?  Is there any reason not to permit a
trailing dot in 5321-bis to bring it in line with DNS rules?

John Levine, johnl(_at_)iecc(_dot_)com, Primary Perpetrator of "The Internet 
for Dummies
Information Superhighwayman wanna-be,, ex-Mayor
"More Wiener schnitzel, please", said Tom, revealingly.

* - no, really

        Dotless hostnames are in the local namespace and can *never*
        be made to work *reliably* in a global context.

        Note the use of non-heirachical names is undoing the changes
        introduced by RFC 921 and will introduce problems RFC 921
        was trying to remove/prevent.

Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews(_at_)isc(_dot_)org

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