when using safelinks ATP how do you whitelist a mailto link

We are trying to create an approval process using service manager. The link to approve is 

<a href="mailto:helpdesk@company.com?subject=something&body=[approved]">[approved]
</a>

So in the email body just contains a mailto link that opens another new email with the defined subject and body of email.

But ATP safelinks is re-written the mailto link and when you link on it a browser window opens with a error "can't reach this page"

How can I whitelist a mailto link?