52.23.133.255.
Question and response
Question
dig mail.captcolo.com. PTR
Answer
mail.captcolo.com. 300 PTR 52.23.133.255.
Authority
captcolo.com. 172800 NS ns-1165.awsdns-17.org.
captcolo.com. 172800 NS ns-1552.awsdns-02.co.uk.
captcolo.com. 172800 NS ns-391.awsdns-48.com.
captcolo.com. 172800 NS ns-780.awsdns-33.net.
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0