User research – How can I ask my customers' customers?

We are a SaaS company providing web and mobile apps to our customers. Your customers use our product but do not know that we exist as a business. Now I'm on board as a designer. I would like feedback and thoughts.

Of course, I would have to wind down our customers for something like that, but does anyone have any experience with how to make surveys in this situation?

Ideally, I would like to have not only the survey in the app, but also the ability to send surveys by e-mail.