mta-1.delta.gr-mail1.com has no MX records.
Question and response
Question
dig mta-1.delta.gr-mail1.com. MX
Answer
The response has no answer records.
Authority
gr-mail1.com. 180 SOA ns0.dnsmadeeasy.com. dns.dnsmadeeasy.com. 2008010213 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0