Electronic mail systems are either computerized or noncomputerized. Important among the computerized systems are the (36) ones organized into (37) of various sizes. Most noncomputerized electronic mail systems such as (38) units of various kinds are simple, turnkey systems that require little effort to (39) .Though often of value in (40) applications, these systems have only interim (间歇) worth in office automation (41) they can be electronically integrated.
Communication in an EMS is either synchronous or nonsynchronous. People involved in synchronous communication must (42) be at the same absolute time, such as (43) a telephone call. A nonsynchronous system (44) at different times.
Electronic systems output soft copy or hard copy. Soft copy (45) , but many applications will (46) .