IM2000 could've been a reasonable step in shifting costs towards those generating them, especially in the earlier-environment in which it was proposed - when ba

IM2000 could've been a reasonable step in shifting costs towards those generating them, especially in the earlier-environment in which it was proposed - when bandwidth & storage were more salient bottlenecks. Sure, there would still be a (smaller) pointer (or metadata) saved by the recipient. But such pointers/metadata might've allowed identifying certain originators/remote-stores as sources of unwanted mail, earlier, before transmission/storage elsewhere. That, and the need for senders to provide an enduring server for the mail to be read, could've forced some of the same sender-side stability/reputation that's since become central to mail-delivery, via other mechanisms (DKIM/etc). I'm not sure it was ever much more than a rough concept/prototype, not a complete solution. Its central idea – "reverse the responsibilities" – could still be part of an improved messaging system, even if it doesn't solve everything.