My iPhone wont let me put my hotmail e-mail address on the mail. Why?

I have my yahoo on my mail option, and i see that we can have more than one -mail address but it wont let me add it. how come?
My iPhone wont let me put my hotmail e-mail address on the mail. Why?
hotmail and msn mail can only be checked in safari as you normally do with your computer. they are the only accounts you cannot add in the mail option
Reply:Mayb u dont no waht u doing
Reply:its not compatible