So, at the moment I am signing mails from specific domains using opendkim and this works. But when I try to send mails from domains that opendkim does not know, they they are not signed.
What I want to do, is to make opendkim sign all emails going through postfix using a single domain, just like mailchimp etc is doing.
Example: I am sending emails from email@example.com using mailchimp, and the signeture is something like the following:
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; s=k1; d=mail2.suw13.rsgsv.net; h=Subject:From:Reply-To:To:Date:Message-ID:List- ID:List-Unsubscribe:Sender: Content-Type:MIME-Version; firstname.lastname@example.org; bh=4Rla76/wHV31ER3IZqXOuA09j3OG2SuFbfD5Jc7Kn94=; b=17jmyvz05JfeNC+avqWJmtESF2A58LA/CievFVtQ0sqwo4FYKAP0Gfpjtc5LSG7tr9ntS5CziAgSOa+UyEjRP3AhZOOXDFoQMUG0gntqxg/gP074Vi7Hy0XvFzAiJYZfAhijwvaroY45hjuX+RN3nQ0xTfhWem5mv3+VVYpwvUo=
How do I achieve this?