On Mar 18, 2008, at 11:31 AM, Frank Ellermann wrote:
Steve Atkins wrote:
As the hostname being checked is on the RHS of an email address
there must be an A record or MX record for it, in order for it to
be... operationally relevant, anyway.
JFTR, if all goes well 2821bis will explicitly add AAAA. This does
not mean that "AAAA only" is an operationally good idea today, but
the "MX required" faction was hopelessly outnumbered for 2821bis.
What justifications were given for including AAAA records as SMTP
discovery records in the face of today's level of abuse?
Nevertheless, this outcome does not prevent a requirement for MX
records when publishing DKIM policy. Only MX records are required to
be at the email-address domain and are used specifically by SMTP.
Having the MX record to qualifyuse of email policy can reduce the
number of transactions required for policy discovery, and offers a
practical means to disavow use of DKIM/SMTP.
-Doug
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