http://www.rfc-editor.org/rfc/rfc5173.txt
RFC 5173: Sieve Email Filtering: Body Extension, J. Degener, P. Guenther2008-04-01T23:00:00-00:00This document defines a new command for the "Sieve" email filtering language that tests for the occurrence of one or more strings in the body of an email message. [STANDARDS-TRACK]