Mail::DKIM::DNS - performs DNS queries for Mail::DKIM
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
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, <firstname.lastname@example.org>
Copyright (C) 2006-2007, 2012-2013 by Messiah College
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.