R

recipient
An object in the directory that can receive messages and information. Microsoft Exchange Server recipients are mailboxes, distribution lists (DLs), public folders, and custom recipients.
recipient table
A MAPI object that provides access to information about a message’s recipient list. Each row in the table contains information about one recipient.
remote procedure call (RPC)
A message-passing facility that is independent of the underlying network and allows a distributed application to call services available on various computers in a network. Microsoft Exchange Server uses RPC for client-server communications.