mercutio.ni.caltech.edu has no MX records.
Question and response
Question
dig mercutio.ni.caltech.edu. MX
Answer
The response has no answer records.
Authority
caltech.edu. 900 SOA ns0090.secondary.cloudflare.com. hostmaster.caltech.edu. 2022897899 10800 3600 2592000 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0