StrongMail has always had the ability to add in custom headers since its inception. This mean of course that any customer can take advantage of the List-Unsubscribe header today and it has already been tested in customer situations with success.
You can specify a specific email address to send un-subscription requests to or even use a un-subscription URL if supported by the receiver. The StrongMail platform offers many different methods for allowing end-users to unsubscribe. As customers take advantage of our extensive reporting system which again includes support and reporting of un-subscriptions internally, they can make this a seamless process when combined with the List-Unsubscribe header.
Here is a screenshot one of the ways you can take advantage of the header:
In StrongMail, the unsubscribe system can also generate a personalized and unique unsubscribe option for each email based on the recipient and campaign. You can apply the uniquie option as well for the List-Unsubscribe header by applying "List-Unsubscribe: ##UNSUBSCRIBETAG##" instead in your header options.