Thank you for writing in. Sure - If you do not create an account or use Postman without signing in then we will not collect any of the data. We will only store the actual requests that are sent when the user signs into the application. That said - the data is encrypted in rest and in transit using industry best standard encryption algorithms. Hope this clarifies!
https://www.postman.com/licenses/privacy/
Under "Information you provide to us": Content you provide through our products: The Services include the Postman products you use, where we collect and store content that you post, send, receive and share. This content includes any information about you that you may choose to include: we collect feedback you provide directly to us through the product and we collect clickstream data about how you interact with and use features in the Services.