problems sending to prodigy.net hosted email

Fri Mar 9 21:23:27 UTC 2018

We are having issues with domains hosted on prodigy.net email servers
including att.net, bellsouth.net, and scbglobal.net.

We are being rejected for bad reverse DNS, but DNS is setup correctly. 
The error we are receiving is:
Remote host said: 550 5.7.1 Connections not accepted from servers
without a valid sender domain.flph829 Fix reverse DNS for 74.252.14.252

I leave it up to the reader to test the validity of 74.252.14.252, but
every test we've done looks good.

The MX records for these domains indicate this (identical on the three
domains mentioned above):
;; ANSWER SECTION:
att.net.        175    IN    MX    5 al-ip4-mx-vip1.prodigy.net.
att.net.        175    IN    MX    5 ff-ip4-mx-vip2.prodigy.net.
att.net.        175    IN    MX    5 ff-ip4-mx-vip1.prodigy.net.
att.net.        175    IN    MX    5 al-ip4-mx-vip2.prodigy.net.

Everything we can find on the postmaster pages, forums, etc. point to
emailing abuse_rbl at abuse-att.net.  We have done this and received their
autoresponder.  We've waited the requisite 48 hours and emailed again
for an escalation only to receive another autoresponder with another
ticket number attached (even though we emailed with a ticket number in
the message).    This has now been ongoing since at least March 4, when
we received our first complaint and we have yet to hear anything from
AT&T.   We don't currently have any direct contacts for Prodigy.net.

I will say that the 75.252.14.0/24 netblock is owned by AT&T and I'm
wondering if that might be causing the issue.  For instance, they are
trying to do a local lookup of the PTR record instead of contacting the
delegated servers.

I'm hoping someone here has a point of contact which I might reach out
to in order to correct this issue.  Any help would be appreciated.

Trey Nolen