A New Internet-Draft is available from the on-line Internet-Drafts directories.
Abstract: ‘With “refuse”, Sieve gains the ability to simply not accept an email during the SMTP transaction (instead of accepting it and then sending an MDN [MDN] back to the alleged sender using “reject”). A Joe-job is a spam run forged to appear as though it came from an innocent party, who is then generally flooded by the bounces, MDNs and messages with complaints. With “reject”, MDNs contribute to the flood of Joe-job spam to victims of Joe-jobs; SMTP level refusals usually don’t. So “refuse” provides users the latter method to handle unwanted email.’
http://www.ietf.org/internet-drafts/draft-elvey-refuse-sieve-00.txt