Does anyone know if there any special requirements that state banks have to use a return service requested envelope? The bank I work at now uses those envelopes for everything they mail out, so nothing gets forwarded onto the customers.

It's been a long time since I've looked into this but I believe this is a bank decision. We use "Forwarding Service Requested" on our envelopes. If memory serves, the fees from the post office vary depending on which type of service you use.