Does smartphone have "New Button"?

I found a page "The NewMenuX Example" in sp2003se SDK documents, and some thing familiar in wm5 for smartphone SDK documents too.

I know there is a "New Button" on Pocket PC's desktop toolbar. Does smartphone has it
When a new mail comes, the second desktop toolbar button(right soft key button) becomes "Message". Is this function implemented by using the "New Button"

I wan't to implement this function in my own application. But I have no Idea on it.