~/src $ host 37.120.193.122
   Host 122.193.120.37.in-addr.arpa. not found: 3(NXDOMAIN)
   ~/src $ host [1]twfno.gf
   Host [2]twfno.gf not found: 3(NXDOMAIN)
   ~/src $ host [3]google.com
   [4]google.com has address 172.217.164.174
   It says it's rejecting the email due to being relayed by the ip above,
   but my dns doesn't appear to even know that you exist.  Wasn't active
   in it enough to try Tor.

References

   1. http://twfno.gf/
   2. http://twfno.gf/
   3. http://google.com/
   4. http://google.com/