spf3.flexential.com has no MX records.
Question and response
Question
dig spf3.flexential.com. MX
Answer
The response has no answer records.
Authority
flexential.com. 3600 SOA ns1.peak10.com. dev-notices.peak10.com. 2018011800 3600 1200 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0