#!/usr/bin/perl
use warnings;
use strict;
use IO::Socket::INET;
use File::Basename;
use Net::Domain qw(hostfqdn hostdomain);
use Net::DNS;
use Data::Dumper;

if(@ARGV != 1) {
  print "usage: ", basename($0), " <emailaddress>\n";
  exit;
}

autoflush STDOUT 1;

sub post {
  my $socket = shift;
  my $command = shift;
  my $ret;

  print " >> $command";
  print $socket $command;
  while ($ret = $socket->getline) {
    print "<<  ".$ret;
    $ret =~ /[0-9]([- ]).*/;
    last if ($1 eq " ");
  }

}

my $email = $ARGV[0];
$email =~ m/.*@(.*)/;
my $domain = $1;

print "Getting MX for $domain\n";
my @mx = mx($domain);

print "Connecting to ".$mx[0]->exchange."\n";
my $socket = IO::Socket::INET->new(
  PeerAddr => $mx[0]->exchange,
  PeerPort => 25,
  Proto => "tcp") || die "Error: couldn't create socket.";

print "<<  ".$socket->getline;
post $socket,"EHLO ".hostfqdn()."\r\n";
post $socket, "MAIL FROM:<>\r\n";
post $socket, "RCPT TO:<$email>\r\n";
post $socket, "QUIT\r\n";