unqualified domains, was ICANN to allow commercial gTLDs

Jay Ashworth jra at baylink.com
Mon Jun 20 17:42:09 UTC 2011

----- Original Message -----
> From: "Tony Finch" <dot at dotat.at>

> Trailing dots are not permitted on mail domains.

I couldn't believe that, so I went and checked 5322.  Tony's right: 
there is no way to write an email address which is deterministic,
unless mail servers ignore the DNS search path.  At least, that's 
what it sounds like to me.

> There has been an ongoing argument about the interaction between
> unqualified domains and TLDs in mail domains. RFC 2821 said
> single-label mail domains were syntax errors, but this was probably an
> editorial mistake and RFC 5321 permits them. It's probably safest to
> assume that a single-label mail domain is a local unqualified domain
> which will have its qualifying labels appended by the message
> submission server, and in other contexts all bets are off.

In fact what matters is what the processing rules and code of mail servers
*do* with monocomponent RHSs.  Do they try to apply the server's DNS
search path to them?  Or whatever's in their configs?  Or do they just
try to look them up in DNS, monocomponent.

-- jr 'Eric Allman, Wietse Venema, DJB; please pick up the courtesy phone' a
Jay R. Ashworth                  Baylink                       jra at baylink.com
Designer                     The Things I Think                       RFC 2100
Ashworth & Associates     http://baylink.pitas.com         2000 Land Rover DII
St Petersburg FL USA      http://photo.imageinc.us             +1 727 647 1274

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