http://www.rfc-editor.org/rfc/rfc5703.txt
RFC 5703: Sieve Email Filtering: MIME Part Tests, Iteration, Extraction, Replacement, and Enclosure, T. Hansen, C. Daboo2009-10-01T23:00:00-00:00This document defines extensions to the Sieve email filtering language to permit analysis and manipulation of the MIME body parts of an email message. [STANDARDS-TRACK]