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.
R's,
John
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