fixing the issue that returns a help page if the IP is blocked: http://postmaster.yahoo.com/550-bl23.html. there is a "550" in the name of the page which makes us think that the address doesn't exist where in fact, yahoo has blocked the IP. In this case, we should emit undetermined and not false
Merge pull request #18 from faridfadaie/master

fixing the issue that returns a help page if the IP is blocked: http://p...