mx01.office.is has no CNAME records.
Question and response
Question
dig mx01.office.is. NS
Answer
The response has no answer records.
Authority
office.is. 10800 SOA ns01.office.is. cpanel.premis.is. 2026022301 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0