how to create a lead/contact from the auto-email after submission of a web-to-case form?

how to create a lead/contact from the auto-email after submission of a web-to-case form?

when the form web-to-case on our website is filled out a notification is generated to inform us of the new case.
We can't generate a lead/contact as the email comes from  systemgenerated@zohocrm.com. Only later - manually - we can generate a new contact or simply adds the case to an existing account.

Doing the same from the email would be faster and better because we can activate a task as well.

Any suggestion how to do it, please?