Lmail1.london.integral.com.253.74.64.in-addr.arpa has no NS records.
NS records for this zone are defined at 253.74.64.in-addr.arpa.
NS records for this zone are defined at 253.74.64.in-addr.arpa.
Question and response
Question
dig Lmail1.london.integral.com.253.74.64.in-addr.arpa. NS
Answer
The response has no answer records.
Authority
253.74.64.in-addr.arpa. 43200 SOA ns-a.pnap.net. hostmaster.pnap.net. 2009031200 28800 1800 604800 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0