Even better. To get the mailserver, something like this (with your added sanity and error-checking):

use strict;
use Net::DNS;
my ($domain) = $email_to =~ /@(.*)$/;
my ($mailserver) = map { $_->exchange } sort { $a->preference <=> $b->
+preference } mx($domain);
[download]

This gets the most preferred mailserver. Alternately, you might want to loop the array by preference, exiting on success.