Changing Reply Email and Customizing Form Emails

Not everything is a marketing and sales situation. We need this exact solution as the trigger/ticketing with external systems is often driven by sending an email to a set address and the tracking is established by who the email was sent from and thus, I need to be able to capture information from a form submittal and resend to the external systems email we have used for years, but is must seem to come from the same email/contact that submitted it which starts the process in the external system for which there are no Apps, etc to tie it in and an API is overkill.