MX Record Lookups

[Gerard]

Morning all, good to see you.
I have some nasty code here which I wrote a while back to do MX record lookups. It actually works, but I was just looking at it, and realised it was a bit nasty: there must be a better way. I am still really bad at regular expressions... Here is some code

use Net::DNS::Resolver;
use Net::DNS::RR;
use Net::DNS::Packet;
use strict;

#Takes an email address and returns the 
#mx record (uri of the smtp server that looks after this domain) as a 
+string
sub mxLookup(){

   #extract the domain from the email address
   my ($email) = @_;
   my @parts = split(/\@/, $email);
   my $domain = @parts[1];

   #Create a DNS Resolver and request records of type MX
   my $server;
   my $res = new Net::DNS::Resolver;
   $res->nameservers("202.27.184.3", "202.27.184.5", "203.96.152.4", "
+203.96.152.12");
   my $packet = $res->send($domain, "MX") || return "error";

   #Parse the results to get the preferred smtp server for this domain
   my $answer = $packet->string;
   my $answerSection = ";; ANSWER SECTION";
   my @results;
   @results=split(/$answerSection/, $answer); 
   @results=split(/;;/, $results[1]);
   @results=split(/\)\n/, $results[0]);
   @results=split(/\n/, $results[1]);
   my $priority = "99999999999";

   foreach(@results){
      my @results2=split(/\t/, $_);
      my @results3=split(/ /, $results2[4]);
      if ($results3[0] < $priority){
         $server = $results3[1];
      }
  }
  if (!$server){
      return "error";
  }
  return $server;
}

Any ideas?
Regards,
Gerard

[rob_au]

This can be done a lot easier using other Net::DNS::Packet and Net::DNS::RR methods ...

my $packet = $res->send($domain, 'MX');

foreach my $answer ($packet->answer) {

    next unless $answer->type eq 'MX';
    push @results, $answer->exchange;
}

Additionally, depending upon your requirements, it may be worthwhile to return a list of mail exchanges ($answer->exchange) and their respective preferences ($answer->preference).

[Gerard]

hmmmm.... Why couldn't I find that when I was writing the code. I seem to remember pouring over it for quite some time.
Thanks for your help
Regards,
Gerard

[Zaxo]

The Net::DNS module wraps much of that for you - no need to rewrite all of it. After the Net::DNS docs:

use Net::DNS;
my @mx = mx($domain);

, minimally, or

use Net::DNS;
my $resolvewr = Net::DNS::Resolver->new();
my @mx = mx $resolver, $domain;

which allows for error handling and other tricks.

[grinder]

<merlyn type="shameless-plug">I already have code to do that.</merlyn>

You might be interested in looking at mx - Mail Exchanger (MX) information about internet hosts. I use this regularly to help me track down various smtp hackery foolery.

[sunadmn]

This looks a bit ugly like you said and I would suggest using Net::Nslookup it will return exactly what you need with half of the code. I have just finished a project doing the same and this worked awsome.

Sunadmn
USE PERL