Unable to find any PTR-records for the specified domain/ip :(
Log
+000
Resolving PTR record of '54.239.99.0'
+054
ERRNo PTR record availible DNS server 'pdns6.ultradns.co.uk' raised an NotExistentDomain error, while beeing queried for PTR-records on domain '0.99.239.54.in-addr.arpa'.