With this Add-on for Super Forms you can subscribe users for Mailster after a user submits the form. Optionally let users select their interests (Lists), and save custom fields set within your Mailster configuration.
Demo https://codecanyon.net/item/super-forms-mailster-addon/19735910
Downloadhttps://www.filecad.com/ihnL/Super-Forms---Mailster-Add-on-v1.0.2.rar