Do you only do email surveys, or can I do these within my own website?
We do have the option to do in-app NPS. It's a little bit trickier to set up, and we often find that sometimes the response rates are not as good as email, because we may be interrupting your user in the middle of a task.
If you're wanting to do in-app surveys, have a think about the best time to ask your users (maybe after checking out?), and get in touch with us.