mail7.vnslns.com has no MX records.
Question and response
Question
dig mail7.vnslns.com. MX
Answer
The response has no answer records.
Authority
vnslns.com. 3600 SOA pns31.cloudns.net. support.cloudns.net. 2025020607 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0