mail1.otmltd.com has no CNAME records.
Question and response
Question
dig mail1.otmltd.com. NS
Answer
The response has no answer records.
Authority
otmltd.com. 937 SOA ns1.virginmedia.net. hostmaster.virginmedia.net. 2025121703 86400 7200 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0