Mail::DKIM::DNS - performs DNS queries for Mail::DKIM


version 1.20230911


This is the module that performs DNS queries for Mail::DKIM.


This module has a couple configuration settings that the caller may want to use to customize the behavior of this module.


This global variable specifies the maximum amount of time (in seconds) to wait for a single DNS query to complete. The default is 10.


Use this global subroutine to get or replace the instance of Net::DNS::Resolver that Mail::DKIM uses. If set to undef (the default), then a brand new default instance of Net::DNS::Resolver will be created the first time a DNS query is needed.

You will call this subroutine if you want to specify non-default options to Net::DNS::Resolver, such as different timeouts, or to enable use of a persistent socket. For example:

  # first, construct a custom DNS resolver
  my $res = Net::DNS::Resolver->new(
                    udp_timeout => 3, tcp_timeout => 3, retry => 2,

  # then, tell Mail::DKIM to use this resolver


This is a convenience subroutine that will construct an appropriate DNS resolver that uses EDNS0 (Extension mechanisms for DNS) to support large DNS replies, and configure Mail::DKIM to use it. (As such, it should NOT be used in conjunction with the resolver() subroutine described above.)


Use of EDNS0 is recommended, since it reduces the need for falling back to TCP when dealing with large DNS packets. However, it is not enabled by default because some Internet firewalls which do deep inspection of packets are not able to process EDNS0-enabled packets. When there is a firewall on a path to a DNS resolver, the EDNS0 feature should be specifically tested before enabling.


  • Jason Long <>

  • Marc Bradshaw <>

  • Bron Gondwana <> (ARC)


Work on ensuring that this module passes the ARC test suite was generously sponsored by Valimail (


  • Copyright (C) 2013 by Messiah College

  • Copyright (C) 2010 by Jason Long

  • Copyright (C) 2017 by Standcore LLC

  • Copyright (C) 2020 by FastMail Pty Ltd

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.6 or, at your option, any later version of Perl 5 you may have available.