Quite some time ago I wrote up Basic DNS: PTR records and why you care. I realized today that it is far
too geeky: I sent someone experiencing a PTR issue to read that and
he came back still thinking that either his Mac or Verizon were to blame.
Why does he think that? Well, I suspect mostly because he got bad support
from Verizon AND Apple. His problem was that email he sent to someone
with a Comcast address got bounced back with a message like this:
Comcast requires that all mail servers must have a PTR record with
a valid Reverse DNS entry. Currently your mail server does not fill
Whose mail server does not fill that requirement? His Mac Mail.app is set to use "outgoing.verizon.net"
as its outgoing server. His machine NEVER TALKED TO COMCAST. It's not
supposed to: it's supposed to talk to "outgoing.verizon.net". It's
THAT machine or some other machine of Verizon's that will talk to Comcast. So
if Comcast is complaining, it's something at Verizon they are complaining about,
and nothing to do with whether or not he's using a Mac or a PC!
It's beyond amazing that no one at Apple or Verizon was able to
help him with this and that they each kept bouncing him back to
Specifically, Comcast rejected "18.104.22.168". I just checked and
that's NOT "outgoing.verizon.net" but it is in Verizon's block, and
it doesn't have a PTR record so Comcast is right to complain. Verizon
needs to assign a PTR to that address and that wll be the end of
Nothing to do with OS X or anything else. Just Verizon itself.
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