kalob3: DKIM/Domain Keys Signature?

[Johannes Graumann]

Hello,

I have been testing a kolab3/Debian wheezy set up using 
http://www.allaboutspam.com/email-server-test

One of the comments that comes back is:
> Email does not contain any DKIM/Domain Keys Signature and the published
> Domain Keys policy does not specify whether to accept or reject unsigned
> Emails. Signing your Outbound emails and clearly specifying a policy to
> accept signed emails will minimize chances of your Email being considered
> as SPAM. 

To the experienced admins here: is this worth implementing? And if so: what 
might an implementation (preferably on Debian) look like and consist from?

Thanks for your input.

Sincerely, Joh