Can I upgrade to the Lion Mail app alone, without upgrading to Lion in general? I'm currently on 10.6 and I really like it so I'm not really thinking about an upgrade right now. Two things I really like about 10.7 are the full screen apps and the Mail client.

Is it possible to somehow upgrade/purchase the Mail client of 10.7 alone? It would be really nice if I could do that.
These apps (and the full screen mode) require APIs that are not available on versions prior to Lion. Even if one could purchase Mail separately, it wouldn't run.