This article is from the LAN Mail Protocols FAQ, by John Wobus firstname.lastname@example.org with numerous contributions by others.
ACAP (Application Configuration Access Protocol), formerly IMSP
(Interactive Mail Support Protocol), is a protocol which is being
developed to compliment IMAP4 by offering related e-mail services
beyond the scope of IMAP4. It includes the ability to subscribe find &
subscribe to bulletin boards, mailboxes, and to find and search