--On Friday, 21 April, 2006 21:44 -0700 Yuri Inglikov
There appears to be some disconnect between ABNF syntax and a
prose. I.e. it appears that ABNF requires at least 2
sub-domain parts, while prose discusses "one or more
dot-separated components". Which one is "more correct" and any
scenario when a single-component domain name can be valid /
useful in modern SMTP?
Domain = (sub-domain 1*("." sub-domain)) /
address-literal sub-domain = Let-dig [Ldh-str]
Note that this pair of productions have been tentatively changed
Domain = (sub-domain 1*("." sub-domain) ["."] ) /
in draft-klensin-rfc2821bis-00.txt, posted July 2005 and now
presumably expired. After some discussion (many months prior to
this posting), the working draft for -01 has been tentatively
modified require the trailing period in the second case and to
explain the situation in the paragraph you cite.
This issue again emphasizes the reasons why it would be
desirable to get out a clean revision/update to RFC2821. But
that target is impossible if any discussion is going to be
overwhelmed by arguments about anti-spam measures and how email
might work better if fundamental principles were changed.