efolder.mktoweb.com has no MX records.
Question and response
Question
dig efolder.mktoweb.com. MX
Answer
The response has no answer records.
Authority
mktoweb.com. 900 SOA ns1.marketo.com. ops.localhost. 338789274 300 300 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0