spfext2.rice.edu has no MX records.
Question and response
Question
dig spfext2.rice.edu. MX
Answer
The response has no answer records.
Authority
rice.edu. 3600 SOA ns1.rice.edu. hostmaster.rice.edu. 2023366876 14400 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0