Microsoft is going to add restrictions and rights to Outlook, like who can receive and forward mail, as well as what we discussed yesterday, email that expires and disappears.
This should scare you. It's billg's tactic to co-opt email. Basically, after a while, after enough proprietary extension, e-mail will become part of the Windows platform, because non MS systems won't be able to offer the same functionality as Outlook. This is the worst case. The medium case is that stratified networks appear: Outlook users and non-Outlook users, who have trouble mailing each other. The best case is that it fails miserably.
Is the tactic feasible? It depends. If people find the restrictions useful, the market will tip fast, because of network effects.
I suspect that the value of having a universal, cost-free standard for email outweighs the benefits Microsoft wants to provide. But it's a tactic that has essentially zero cost and infinite upside to Microsoft, so they'll push this for quite a while.