How can we redirect customers to their own page at our site?

For each client sign in, they will be redirected to their own page. In the event someone who has not been entreated into the system tries to login, is there some sort of error message that comes up?

As far as I understood your idea, I can assume that you are trying to create a Login form with JotForms. In case I am right, I should warn you that this is not compliant to JotForm Terms-of-Use, because is considered as phishing. You can check this thread for more information.

Despite that, if your sign-in form remains the same (filtering customer's emails), it can work. 

Even though, I have doubts as to how create "their own page" at your website. I can only suggest creating a list of customers, who would be redirected to a particular page of your website. If this is acceptable for you, please look through the following guide to get more information as to redirecting based on a condition:

Change-Thank-You-Page-URL-Based-on-a-Condition

Hope this helps! But, please get back to us if you need further assistance.