51.83.21.64.ip.letsignit.com has no SRV records.
Question and response
Question
dig 51.83.21.64.ip.letsignit.com. SRV
Answer
The response has no answer records.
Authority
letsignit.com. 10800 SOA ns1.gandi.net. hostmaster.gandi.net. 1772064000 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0