A New Internet-Draft is available from the on-line Internet-Drafts directories.
Abstract: «This memo defines an extension to the SMTP submission protocol for client indication of a future-delivery time. This extension permits a client to use server-based storage for a message that should be held in queue until an appointed time in the future. This is useful for clients which do not have local storage or are otherwise unable to release a message for delivery at an appointed time.»
http://www.ietf.org/internet-drafts/draft-vaudreuil-futuredelivery-02.txt