Add List-Unsubscribe Email Header?
Is there anyway to add/edit our email headers? I am not talking about the top of the HTML document, but the actual header information of the email (reply-to, etc.)
I know that the Email Editor gives Me Accress to From & Reply-to, but I have been advised that adding a List-Unsubscribe Header would possibly increase our deliverability with GMail, Outlook.com, and others.
Does Anyone know if this can be added?