edu has no MX records.
Question and response
Question
dig edu. MX
Answer
The response has no answer records.
Authority
edu. 900 SOA a.edu-servers.net. nstld.verisign-grs.com. 1772223571 1800 900 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0