http://www.rfc-editor.org/rfc/rfc2359.txt
RFC 2359: IMAP4 UIDPLUS extension, J. Myers1998-06-01T23:00:00-00:00The UIDPLUS extension of the Internet Message Access Protocol [IMAP4] provides a set of features intended to reduce the amount of time and resources used by some client operations. [STANDARDS-TRACK]