Updating exising deliveries with list-unsubscribe
Hi everyone,
we are looking to update our deliveries for list-unsubscribe functionality. I have tested and have this working in a new template for future deliveries, unfortunately we have a large number of currently running ongoing campaigns that will need this function as well. is there any way to update the 'Additional SMTP headers' field for this in existing deliveries?
thanks in advance,
Matt