incoming2021.csail.mit.edu has no MX records.
Question and response
Question
dig incoming2021.csail.mit.edu. MX
Answer
The response has no answer records.
Authority
csail.mit.edu. 900 SOA auth-ns0.csail.mit.edu. bug-domain.csail.mit.edu. 253605279 1800 300 604800 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0