Unable to find any PTR-records for the specified domain/ip :(
Log
+000
Resolving PTR record of '173.231.90.0'
+255
ERRNo PTR record availible DNS server 'ns-263.awsdns-32.com' raised an NotExistentDomain error, while beeing queried for PTR-records on domain '0.90.231.173.in-addr.arpa'.