--On Friday, March 23, 2007 00:03 +0100 Frank Ellermann
<nobody(_at_)xyzzy(_dot_)claranet(_dot_)de> wrote:
We could argue forever about this, some folks elsewhere
even think it's a good idea to modify ABNF discussed for
years in AUTH48, but actually you've only three choices:
1: Allow the trailing dot everywhere no matter what 2821
and 2822 say. Maybe say "SHOULD have a dot" for TLDs.
2: Keep it as is in 2821, no trailing dots, and one dot
required. This excludes TLDs, unlike (2)822.
3: Same as (2) with a special rule for TLDs: TLDs MUST
have the trailing dot, other domains MUST NOT have the
trailing dot.
The 3rd choice is not KISS, and it has a high astonishing
factor. Excluding TLDs in the 2nd choice is also somewhat
astonishing, my question about it (2004-11-12) was if this
is a typo, and you said "intentional". 1st and 2nd choice
are KISS.
There is a fourth possibility and it seems to be where we are at
present. That is:
4) One-label names permitted, no trailing dot ever. If a
single label name is used, it represents a TLD if sent between
SMTP servers. In input to a submission server, the client must
agree with the server on some method to distinguish between an
incomplete domain name and a TLD. Several such methods are
possible; all are outside the scope of this specification.
john