The Actor Model attempts to be as general as possible to support direct modeling and efficient implementation of all digital computation. For example, an Actor

The Actor Model attempts to be as general as possible to support direct modeling and efficient implementation of all digital computation. For example, an Actor is not required to have an external mailbox, which is required for communication in Erlang [Armstrong, et. al. 1992]. Requiring an external mailbox is problematical for Actors because the mailbox would itself necessarily be another Actor thereby immediately leading to an infinite regress. Also, requiring the use of external mailboxes can slow requests between Actors because it would always be necessary to first deposit a request in an Actor’s external mailbox so that the request could later be retrieved. That a request is almost always sent and received without ever residing in persistent storage, where it can be left and later retrieved, is an important engineering goal for Actors.