_spf3.titan.email has no MX records.
Question and response
Question
dig _spf3.titan.email. MX
Answer
The response has no answer records.
Authority
titan.email. 900 SOA ns-451.awsdns-56.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0