161.mail2world.com has no MX records.
Question and response
Question
dig 161.mail2world.com. MX
Answer
The response has no answer records.
Authority
mail2world.com. 300 SOA mwdns10vmoc.mail2world.com. dns_admin.mail2world.net. 2016043392 3600 300 1814400 300
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0