On 05/08/2013 08:03 PM, Stan Hoeppner wrote:
On 5/7/2013 5:36 PM, /dev/rob0 wrote:
...
Peter has explained this: you indeed seem to have FCrDNS, just not

Maybe my understanding of the definition of Forward Confirmed reverse
DNS is incorrect.  I thought the definition of FCrDNS is that that the
forward and reverse names not only exist but also match.  Apparently
they both must simply exist.

No, they have to match, I'll go into detail so that hopefully you understand...

Your host claims to be greer.hardwarefreak.com and connects from the IP 65.41.216.221, so first we do a lookup on your hostname:

greer.hardwarefreak.com. 3448    IN    A    65.41.216.221

...it matches the IP of your connection ... This is good.

Next we do a reverse lookup on the IP:

221.216.41.65.in-addr.arpa. 86176 IN    PTR    
mo-65-41-216-221.sta.embarqhsd.net.

This doesn't return your initial hostname, but that's ok because that is not specifically required for FCRDNS. What is required at this stage is that the PTR lookup return a valid FQDN and it does indeed.

Note that the FQDN that is returned "looks" like a generic ISP-assigned hostname (because of the IP address in the name). This isn't a good thing and there are some mail hosts that will reject based on this, but very few in my experience. That generic-looking hostname does not mean that it won't pass FCRDNS, though.

Ok, next we do a lookup on the hostname we got back from the previous step:

mo-65-41-216-221.sta.embarqhsd.net. 86166 IN A    65.41.216.221

...this returns your IP address as well, and that is good because this is required for FCRDNS.


Peter

Reply via email to