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Re: [ietf-smtp] Dotless domains and email

2013-07-14 02:33:06
Hi John,
At 15:26 13-07-2013, John Levine wrote:
Depends whether the topic is "dotless domains suck" or the more
general but more important "local namespaces on the Internet and why
the global DNS has to stay out of them."

The usual way is to have "dotless domains considered harmful".

The problem with dotless domains and the problem with whatever.corp or
whatever.lan or whatever.local are really the same: these are
namespaces that have historically been informally managed on
innumerable private networks, often behind firewalls or NATs, and if
you try to use them as global domain names, Bad Things(tm) will
happen.

Yes.

In both cases you can argue, more or less credibly, that it's sloppy
software that would never have done that if it strictly followed the
RFCs, and in both cases the reality on the ground is that it happens
and it's not going to stop.

It is difficult to argue on technical grounds that it should not be done as this is more about assumptions instead of a rule in standards which prohibit the software from handling dotless domains.

The question which was asked is whether dotless domains will, for example, work with email. The initial comment from Dave Crocker, on this thread was "I'm not seeing this requirement/limitation in RFC 5321. It merely requires an FQDN." You mentioned on this thread that there are some ccTLDs which have a MX RR at the top-level.

Some of the problems that can be encountered are visible at the application level. As a matter of convenience a person might type user@example as the recipient address and the software converts that to a FQDN.

draft-moonesamy-dotless-domains-00 [1] discusses about the case of dotless domains. I listed two arguments in Section 6 of the draft. Section 4.4 may be of interest to the people reading this mailing list.

Regards,
S. Moonesamy

1. http://tools.ietf.org/html/draft-moonesamy-dotless-domains-00
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