Yes, 200response.mx can receive emails.
Yes, 200response.mx seems to be a legitimate domain.
A record
13.249.44.79
MX records
alt1.aspmx.l.google.com
64.233.186.26
alt2.aspmx.l.google.com
172.253.116.26
aspmx.l.google.com
173.194.208.27
aspmx2.googlemail.com
64.233.186.26
aspmx3.googlemail.com
172.253.116.26