A New Internet-Draft is available from the on-line Internet-Drafts directories.
Abstract: «Various mailing lists modify the Subject: header field of messages sent to the list to contain a kind of identifier enclosed in square brackets. Every now and then this “feature” is also requested for the main IETF list. This document collects pros and cons of this approach, tries to identify the real issue and will, in a later stage, try to give a recommendation.»
http://www.ietf.org/internet-drafts/draft-koch-subject-tags-considered-00.txt