Code:

###################### 0verCheck ###################
# Coded by The X-C3LL (J.M. Fernández)             #
# Email: overloadblog////hotmail////es             #
# Blog: 0verl0ad.blogspot.com                      #
# Twitter: https://twitter.com/TheXC3LL            #
######################  v0.1  ######################


use Net::DNS;
use IO::Socket;
use Getopt::Long;

GetOptions(
      "list=s"=> \$flag_list,
      "email=s"=> \$flag_email
         );



if ($flag_email) {
   @correo = split("@", $flag_email);
   $server = MX_it($correo[1]);
   print $flag_email." -- ".check($server, $flag_email)."\n";
}

if ($flag_list) {
   open(FILE, "<", $flag_list);
   @lista = <FILE>;
   close(FILE);
   foreach $account (@lista) {
      chomp($account);
      @correo = split("@", $account);
      $server = MX_it($correo[1]);
      print $account." -- ".check($server, $account)."\n";
   }
}

sub MX_it {
   $domain = $_[0];
   $resolver = Net::DNS::Resolver->new;
   @mx = mx($resolver, $domain);
   if (@mx) {
      return $mx[0]->exchange;
   } else {
      return "ERROR MX Not Found";
   }
}

sub check {
   $server = $_[0];
   $account = $_[1];
   @email = split("@", $account);
   $socket = IO::Socket::INET->new(
               PeerAddr => $server,
               PeerPort => 25,
               Proto => 'tcp'
   );

   unless ($socket) { return "ERROR";}

   print $socket "HELO $email[1]\r\n";
   $answer = <$socket>;
   print $socket "MAIL FROM: <test@".$email[1].">\r\n";
   $answer = <$socket>;
   print $socket "RCPT TO: <".$account.">\r\n";
   $answer = <$socket>;
   $answer = <$socket>;
   if ($answer =~ /250/) {
      return "OK!";
   } else {
      return "FALSE!";
   }
}