mailb.m1.maas360.com has no MX records.
Question and response
Question
dig mailb.m1.maas360.com. MX
Answer
The response has no answer records.
Authority
m1.maas360.com. 300 SOA a1-64.akam.net. hostmaster.m1.maas360.com. 2025071130 3600 600 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0