b.nic.ch has no MX records.
Question and response
Question
dig b.nic.ch. MX
Answer
The response has no answer records.
Authority
ch. 900 SOA a.nic.ch. dns-operation.switch.ch. 2026022420 900 600 1209600 900
Additional
. 0 OPT ; payload 1400, xrcode 0, version 0, flags 0