Cannot send mail from my hotmail account on my iphone 4s

i bought a iphone 4s and set up my hotmail account through the Mail setting - Add accout - Hotmail. I have never been able to send mail through this set up. i have deleted the account and re-setup the account several times and had no success. I am able to recieve email but this is still useless if I cannot reply. Is there anyone else with this problem? can anyone help me?

I love this phone, but this is definately a major downfall and I am really %&#@...... unhappy.