How to do email confirmation in serverless

Hi All,
I got a rookie question here. I am building a restful api based on AWS and it requires user click on a link sent by us in their email and then somehow the one request will be sent to our api and do the token validation.

But the problem is I think the API is protected via IAM, and how can u achieve it by clicking on email?
We do not have a front-end. So i really do not think we can do it. But someone told me it is possible. How do we do this?

Is that possbile for us to do it in serverless?

Any help will be appreciated. Thx