ACAP (Application Configuration Access Protocol) is an internet protocol. It was designed to support remote storage and access of program option, configuration and preference information. It replaces the functionality originally covered by the IMSP protocol, without being specifically tied to email.

ACAP is defined in RFC 2244, co-authored by Chris Newman of Innosoft and John Gardiner Myers of Netscape in 1997.

An ACAP server will listen on TCP/IP port 674, and like IMSP, it follows IMAP command syntax very closely.

Unfortunately, ACAP suffers from a chicken and egg problem; although the protocol is seen as useful, few servers exist so support isn't build into clients. Likewise, with no client support, nobody provides servers.

Project Cyrus provides an implementation of an ACAP server written in SML. A few mail clients such as Eudora and Mulberry support storing preferences remotely via ACAP.

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