Cool, I just happened to notice this while browsing...
From <http://www.iana.org/assignments/sieve-extensions>:
Capability name: vnd.dovecot.* (anything starting with "vnd.dovecot.")
Description: Extends the Sieve language with vendor-defined
functionality specific to the Dovecot Secure IMAP
server (http://www.dovecot.org).
RFC number: Not applicable
Contact address: Stephan Bosch <stephan&rename-it.nl>
Timo Sirainen <tss&iki.fi>
Registration Date: 2008-07-28
Any current plans for it or is it just a placeholder?
