This is a discussion space for a whitepaper I'm putting together on the approach to best practices in implementing SMTP unsubscribe headers in email deliveries.
The straightforward approach is to set it in the delivery template, 'list-unsubscribe' etc.
Using a control typology can be preferable if you're in an environment where users can't be trusted, as part of a broader set of restrictions.
The support has set up the following in our delivery templates:
List-Unsubscribe: <mailto:<%= provider.errorAddress !='' ? provider.errorAddress:delivery.mailParameters.errorAddress %>?subject=unsubscribe<%=escape(message.mimeMessageId) %>>
TenantHeader: <%@ include option='DmRendering_cuid' %>
Affinity: <%= delivery.scheduling.IPAffinity %>
X-cust_MessageID: <%= message.id %>
X-cust_DeliveryID: <%= delivery.id %>
X-cust_IMSOrgID: <%@ include option='IMS_Organization' %>
Hope it helps