Re: e-postage stamps, was Welcome to the new(ish) ASRG list

On 3/16/13 10:42 PM, Rob McEwen wrote:
> On 3/17/2013 1:09 AM, Franck Martin wrote:
>> I'm all for outright blocking on no rDNS but who are these large ISPs?
> I don't have a list off the top of my head... but I did have a friend
> who is an IT guy at a company and where the made some changes to their
> firewall just two weeks ago... which mistakenly caused their exchange
> server's outbound IP to switch to an IP that didn't have rDNS.
> Immediately, there were massive numbers of outbound messages blocked
> across many recipients, including some large ISPs. I didn't make a list,
> but he said, "we're being blocked by this and that"... and I recall
> hearing some "household names". (Also, this wasn't totally scientific
> since you could argue that their IP being "new" might have factored into
> the mix... but they were NOT sending ANY spam at that time!)
>
> Also, I recall a person high up at Cox Communications saying that they
> block on "no rDNS", fwiw.
>

Yahoo, AOL, Cox, and Comcast all block on the combination of any 
significant volume and no rDNS.