mail3.memset.com has no MX records.
Question and response
Question
dig mail3.memset.com. MX
Answer
The response has no answer records.
Authority
memset.com. 2506 SOA ns1.memset.com. hostmaster.memset.com. 1771762515 16384 2048 1048576 2560
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0