$Mail::DKIM::DNS::TIMEOUT¶

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

Mail::DKIM::DNS::resolver()¶

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,
                 );
  $res->udppacketsize(1240);
  $res->persistent_udp(1);
  # then, tell Mail::DKIM to use this resolver
  Mail::DKIM::DNS::resolver($res);

Mail::DKIM::DNS::enable_EDNS0()¶

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.)

  Mail::DKIM::DNS::enable_EDNS0();

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.