---
name: "Mail::DKIM::SignerPolicy"
section: "3pm"
platform: "linux"
package: "perl-mail-dkim"
version: "1.20240923-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Mail::DKIM::SignerPolicy"
---

# Mail::DKIM::SignerPolicy(3pm)

determines signing parameters for a message

## NAME

Mail::DKIM::SignerPolicy - determines signing parameters for a message

## VERSION

version 1.20240923

## DESCRIPTION

A "signer policy" is an object, class, or function used by Mail::DKIM::Signer to determine what signatures to add to the current message. To take advantage of signer policies, create your own Perl class that extends the Mail::DKIM::SignerPolicy class. The only method you need to implement is the **apply()** method.

The **apply()** method takes as a parameter the Mail::DKIM::Signer object. Using this object, it can determine some properties of the message (e.g. what the From: address or Sender: address is). Then it sets various signer properties as desired. The **apply()** method should return a nonzero value if the message should be signed. If a false value is returned, then the message is "skipped" (i.e. not signed).

Here is an example of a policy that always returns the same values:

```
  package MySignerPolicy;
  use base 'Mail::DKIM::SignerPolicy';
  sub apply
  {
      my $self = shift;
      my $signer = shift;

      $signer->algorithm('rsa-sha1');
      $signer->method('relaxed');
      $signer->domain('example.org');
      $signer->selector('selector1');
      $signer->key_file('private.key');

      return 1;
  }
```

To use this policy, simply specify the name of the class as the Policy parameter...

```
  my $dkim = Mail::DKIM::Signer->new(
                  Policy => 'MySignerPolicy',
             );
```

## ADVANCED

You can also have the policy actually build the signature for the Signer to use. To do this, call the signer's **add\_signature()** method from within your **apply()** callback. E.g.,

```
  sub apply
  {
      my $self = shift;
      my $signer = shift;

      $signer->add_signature(
              new Mail::DKIM::Signature(
                  Algorithm => $signer->algorithm,
                  Method => $signer->method,
                  Headers => $signer->headers,
                  Domain => $signer->domain,
                  Selector => $signer->selector,
              ));
      return;
  }
```

Again, if you do not want any signatures, return zero or undef. If you use **add\_signature()** to create a signature, the default signature will not be created, even if you return nonzero.

## AUTHORS

- •

  Jason Long \<jason@long.name\>

- •

  Marc Bradshaw \<marc@marcbradshaw.net\>

- •

  Bron Gondwana \<brong@fastmailteam.com\> (ARC)

## THANKS

Work on ensuring that this module passes the ARC test suite was generously sponsored by Valimail (https://www.valimail.com/)

## COPYRIGHT AND LICENSE

- •

  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.