50.18.205.76.
Question and response
Question
dig mail1.hostid.net. PTR
Answer
mail1.hostid.net. 300 PTR 50.18.205.76.
Authority
hostid.net. 172800 NS ns-1283.awsdns-32.org.
hostid.net. 172800 NS ns-1719.awsdns-22.co.uk.
hostid.net. 172800 NS ns-406.awsdns-50.com.
hostid.net. 172800 NS ns-617.awsdns-13.net.
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0