4.123.100.123.in-addr.arpa.
Question and response
Question
dig mta.securedsigning.com. PTR
Answer
mta.securedsigning.com. 1800 PTR 4.123.100.123.in-addr.arpa.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0