On Sun, 03 Jun 2007 22:30:11 +0100, Douglas Otis <dotis(_at_)mail-abuse(_dot_)org>
wrote:
A query to "." returns a _root_ SOA record with a no answer response.
Each server which might attempt to resolve a "." host name will likely
repeat the mistake. There would be no cached record to lessen the
frequency of these mistakes either. Multiply the mistake by billions of
spoofed messages being sent, and this starts looking more like a DDoS
attack. Any potential for creating a DDoS mechanism, intentionally or
not, is relevant to DKIM. A DDoS concern is very relevant when
considering record searching methods and whether a hostname of "."
safely signals "no service."
Would it work if the MX record pointed to a domain such as nomail.invalid?
That ought to get cached AFAIK.
--
Charles H. Lindsey ---------At Home, doing my own thing------------------------
Tel: +44 161 436 6131
Web: http://www.cs.man.ac.uk/~chl
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