spf-a.rnmk.com has no MX records.
Question and response
Question
dig spf-a.rnmk.com. MX
Answer
The response has no answer records.
Authority
rnmk.com. 900 SOA dnsmasterac01.rightnowtech.com. root.rightnowtech.com. 1769019747 600 180 1209600 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0