Design a paper to email and email to paper system.

I am an attorney and I service the legal needs of prisoners in Florida USA prisons. My clients are not allowed emails and the volume of letters we receive is too much. I want a plan designed to efficiently scan the prisoner mail to PDF and allow us reply with email to snail mail conversion. I have seen several services that offer email to snail mail where the email is printed, folded, stuffed, stamped, mailed with confirmation. google email to snail mail for ideas. Implementation sounds easy but filing and record retention are an issue. I have thought about issuing clients a sheet of bar code labels to place on their letters. Each prisoner has a unique inmate number so automating seems possible. In a way I am seeking a small private post office. Mail to be scanned, routed to client folders, read, replied to, billed for time, replies filed, archived and backed up. I know what I want. Not sure how to get there. I need help to think this through and offer solutions. What programs and hardware is necessary? What would be the flow chart of the process? Then we need testing, implementation, and ongoing administration but these steps depend on the beginning. The successful planner can expect to move onto other steps but bidding at this stage should be confined to planning and processes.