mx-3.sys.kth.se has no CNAME records.
Question and response
Question
dig mx-3.sys.kth.se. NS
Answer
The response has no answer records.
Authority
sys.kth.se. 379 SOA a.ns.kth.se. hostmaster.kth.se. 2026021901 600 600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0