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Re: domain name definition in RFC2821

2007-03-22 18:50:33

--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.