On 11/03/2014 01:52 AM, Lyle Giese wrote:
If the provider won't or is unable to provide reverse for the IPv6
static address you have, it will be sub-optimal for you to continue to
advertise and/or use the IPv6 address for SMTP.
It's all part of the 'prove it's not a dynamic ip address' and part of
the 'proper reverse DNS provides some level of authority/delegation to
use that ip address for legit SMTP usage'.
My SPF record does exactly that: it provides a level of authority for
that particular host to send mail for my domain.
In a much better, finer grained delegation, since a PTR maps to a single
domain, while a SPF specifies exactly *which* domains permit that
particular host to send mail.
The "need a PTR" requirement was created back when SPF was not even a
glint in anybody's eye. While I would prefer to have PTR records for all
my hosts, I don't agree having no PTR merits a clear rejection of a mail
with a valid SPF record for the host.
