c15.blackbaud.net has no MX records.
Question and response
Question
dig c15.blackbaud.net. MX
Answer
The response has no answer records.
Authority
blackbaud.net. 60 SOA ns1.p13.dynect.net. dns.jomax.net. 2023050102 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0