cPanel & Shared Hosting Support

I originally thought that the domainkeys feature within Cpanel was for outgoing email i.e. it would add "DomainKey-Signature" line to the outgoing email headers. For example this is from an email recieved from a yahoo based mailing list:

DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=lima; d=yahoogroups.com;
   b=sB++8MZQVH5dETNpOfS5KlB9VYbRWAF57i3Bdec5zZSRH0mY8grhG2teKMK9o5/dO8IoRENmp7XctchcdAhmkySyGJF0uaJAMfKEi800d2OtU0Kk9+UMGoYG+X9Ntawc;

However, when I enable this feature it appears to make no difference to my outgoing emails, that is, they do not contain a similar line in the email header when sent via an orchard hosted email account, and the feature enabled.

The description of the domain-keys feature within Cpanel reads in a way that suggests that it could be simply to enable checking of in-coming email that use domain keys, rather than anything to so with outgoing email.

Can anyone clarify?

Specifically, I would like to know if it is possible to enable domainkey signing of outgoing email. Also, what the current 'enable domain keys' option actually does.

If you open a support ticket we can check/add the domain key for you.
It's definitely possibly - we often add domain keys for services such as campaign monitor etc

Can you confirm if the feature controlled from cpanel if for incoming mail or outgoing mail?

DomainKeys is an e-mail authentication system designed to verify the DNS domain of an e-mail sender and the message integrity.
So, if you are using external software hosted elsewhere or on your machine to send email, the recipient mail server can check the domain key at the domain host to see if the software is allowed to be sending email on the servers behalf.
So, it's for externally sent email primarily.

http://en.wikipedia.org/wiki/DomainKeys