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Re: [ietf-smtp] Dotless domains and email

2013-06-21 12:55:04
Does anyone have an explanation for the assessment in the ICANN report 
that at least two levels are required?

a) they goofed

2) MTAs running on Unix-ish systems typically use POSIX
gethostbyname() or res_query() to resolve host names.  Most
implementations of those routines when presented with an unqualified
name will first try the name with a locally configured default domain,
and only if that fails will try the bare name.  There is a parameter
in the resolver config file to change that, but I don't know anyone
who changes it.

So it's not in the RFC, but it's sure in the code, and the way it's
implemented, a local host name will mask a dotless TLD, leading to
highly unpredictable results.

The counter-counter argument is that a fair number of ccTLDs have MX
records for the TLD and the world hasn't come to an end, such as the
world's shortest e-mail address n@ai.  For a good time, do an MX
lookup on gt.

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