inf.spectrum.com has no MX records.
Question and response
Question
dig inf.spectrum.com. MX
Answer
The response has no answer records.
Authority
inf.spectrum.com. 14400 SOA auth1.charter.com. hostmaster.charter.com. 2019130041 7200 3600 604800 14400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0