mail1.no-ip.com has no MX records.
Question and response
Question
dig mail1.no-ip.com. MX
Answer
The response has no answer records.
Authority
no-ip.com. 600 SOA ns2.no-ip.com. hostmaster.no-ip.com. 2055708912 600 300 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0