The COMMAND+ extension to the Internet Message Access Protocol [IMAP4] defines a formal syntax for extending [IMAP4] commands. This includes adding requirements on future extensions to the [IMAP4] syntax that may add new commands, so that any command in an [IMAP4] session, be it part of the base-specification, or a current or future extension, can be extended in an arbitrary manner, without conflicts in syntax between current or future extensions.