ns1.marketo.com has no MX records.
Question and response
Question
dig ns1.marketo.com. MX
Answer
The response has no answer records.
Authority
marketo.com. 600 SOA ns1.marketo.com. ops.localhost. 2026020634 900 900 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0