Hello,
i use a PERL script with Mail::SPF to check the SPF-records from received emails. The PERL module seems to have problems with the DNS. After 1-2 min. i get the error: unresolvable name: nameserver at /usr/share/perl5/Mail/SPF/Server.pm line 225

The network and resolf.conf settings from the debian 8 seams to be ok. I have no problems to resolve the IP from google.com or other names. I tried the solution from https://archive.kiza.eu/journal/entry/720 and added a line with localhost in resolf.con, unfortunately this did not help.

This is my code:

#! /usr/bin/perl

use strict;
use Socket;
use warnings;
use Email::Simple;
use DBI;
use File::Copy;
use Date::Parse;
use DateTime;
use Path::Tiny qw(path);
use Mail::DKIM::Verifier;
use Mail::SPF;
use Encode;
use utf8;

open (MESSAGE, "< $ARGV[0]") || die "Couldn't open email $ARGV[0]\n";
       undef $/;
my $raw_email = <>;
close MESSAGE;

my $mail            = Email::Simple->new($raw_email);
my $return_path     = $mail->header("Return-Path");
my $from_header     = $mail->header("From");
my $ip              = $mail->header("X-IP");

my $spf = &spf_check($ip,$return_path);

sub spf_check {

  my ($ip, $domain);
  ($ip, $domain) = @_;

  $domain =~ s/<|>//g;
  $domain =~ s/^.*@//g;

  my $spf_server  = Mail::SPF::Server->new();
  my $spf_request = Mail::SPF::Request->new
    (
      versions        => [1,2],
      scope           => 'mfrom',
      identity        => $domain,
      ip_address      => $ip
    );

  my $return = $spf_server->process($spf_request);

}
[download]

Is the error in my PERL source code or in the system settings of the linux OS?

kind regards
nifu