Scott Kitterman wrote on Wednesday, January 24, 2007 10:58 AM -0600:
On Wednesday 24 January 2007 10:47, Seth Goodman wrote:
I notice that spot checking the IP's from Rene's list shows somewhat
different IP assignments from what they were in Rene's post.
From my checking, each of those server names has two IP addresses
associated with it.
That's right. In addition, some of the IP's that Rene posted now
resolve differently. Comcast appears to shuffle it's server IP's
when needed and without regard for CIDR ranges. While respecting CIDR
ranges would make it easier if they decided to publish SPF, the fact
that they can't easily represent their current sending setup in a
manner that is gentle to their DNS is an adoption hurdle.
I agree that you can make a reasonable argument for networks trying to
aggregate their outbound relays in contiguous IP blocks. It is not
reasonable to argue that those blocks should be CIDR ranges because
IP4 space is too limited. Mail hosts are not the only machines with
externally visible IP's and some of the IP's you would like to juggle
may be under someone else's control.
Sender Policy Framework: http://www.openspf.org/
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