Go to "Messages" and select "Message Templates" from the left-hand menu, where you will see all of your active messages under "Automated". Next, select the message you want to archive. If there are multiple properties under one template, you can remove the property from the "Properties" drop-down list and save the template. Alternatively, if you want to archive the template, select the "Status" drop-down and select "Archived", then "Save Template".

You will then receive a message to confirm the change. Select "Save", and all future scheduled messages will be deleted. The template will still be available under "Archived" in "Message Templates" and can be reactivated at any time.