A new internet-draft is available from the IETF. This draft is a work item of the Sieve Mail Filtering Language Working Group of the IETF.
Abstract: «On email systems that allow for “subaddressing” or “detailed addressing” (e.g., “ken+sieve@example.org”), it is sometimes desirable to make comparisons against these sub-parts of addresses. This document defines an extension to the Sieve mail filtering language that allows users to compare against the user and detail parts of an address.»