Messenger service may be furnished only pursuant to a written agreement between the messenger service company and the institution's customer, under which agreement the messenger becomes the agent of the customer of the institution. The agreement shall further provide that the institution assumes no liability for deposits collected by the messenger from the institution's customers until they are received at an office of the institution and that the institution shall not be liable for cash or other valuables after the institution has delivered them to the messenger for transmission to the customer.
10 Pa. Code § 21.12