#!/usr/bin/perl

use strict;
use Net::DNS;

my $domains = $ARGV[0];
my $nameserver = $ARGV[1];

open(DOMAINS, "< $domains")             or die "can't open $domains: $!";

while(<DOMAINS>){
        my $domain = chomp($_);
        my $domain = $_;
        print "-------------------------------------\n";
        print "Checking domain: $domain\n";

        my $res = new Net::DNS::Resolver;
        $res->nameservers("$nameserver");
        my @mx = mx($res, $domain);
        if (@mx) {
                foreach my $rr (@mx) {
                        my $ip = &lookup($rr->exchange,);
                        print $rr->preference, " ", $rr->exchange, " -> $ip\n";                 }
        }
        else {
                print "can't find MX records for $domain: ", $res->errorstring, "\n";
        }
}
close(DOMAINS)                  or die "can't close $domains: $!";

sub lookup {
        my $domain = $_[0];
        my $res = new Net::DNS::Resolver;
        my $query = $res->search($domain);
        if ($query) {
                foreach my $rr ($query->answer) {
                        next unless $rr->type eq "A";
                        my $rev = &rev_lookup($rr->address,);
                        my $address = $rr->address,;
                        my $lookedup = "$address -> $rev";
                        return $lookedup;
                }
        }
        else {
                return $res->errorstring,;
        }
}

sub rev_lookup {
        my $ip = $_[0];
        my $res = new Net::DNS::Resolver;
        my $query = $res->search($ip);
        if ($query) {
                foreach my $rr ($query->answer) {
                        next unless $rr->type eq "PTR";
                        return $rr->rdatastr,;
                }
        }
        else {
                return $res->errorstring,;
        }
}