Re: Missing ABNF terms in 2821bis?

"Frank Ellermann" <[email protected]>
Newsgroups gmane.ietf.rfc822,gmane.ietf.smtp
Message-ID <[email protected]>
[email protected] wrote:

> Are there corresponding RFCs in the pipe that will allow actually
> doing an MX lookup of such beasts?

No, A, AAAA, and MX names follow the usual LDH-rules.  For UTF8SMTP
it's similar, IDNA and IDNAbis don't permit control codes.

The issue here are hypothetical "domain literals".  The "IPvFuture"
construct in RFC 3986 also doesn't permit control codes.  

Of course you can lookup MX etc. records for names containing any
octet, but that would be no real SMTP MX.  RFC 4408 supports names
derived from local parts in its mechanisms (incl. mx, a, aaaa),
it doesn't allow control codes and dots in directly given labels.

That's admittedly one of the darker corners in the RFC 4408 syntax,
also discussed in <http://www.openspf.org/RFC_4408/Errata>.  

 Frank
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