mu has no MX records.
Question and response
Question
dig mu. MX
Answer
The response has no answer records.
Authority
mu. 3600 SOA v0n0.tld.mu. hostmaster.donuts.email. 1772930907 7200 900 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0