$ host -t mx vuln.ninja
vuln.ninja mail is handled by 10 alt3.aspmx.l.google.com.
vuln.ninja mail is handled by 1 aspmx.l.google.com.
vuln.ninja mail is handled by 5 alt1.aspmx.l.google.com.
vuln.ninja mail is handled by 5 alt2.aspmx.l.google.com.
vuln.ninja mail is handled by 10 alt4.aspmx.l.google.com.