An app has been released on the AppStore that allows you to recieve AND send emails using your hotmail account. It is called mBoxMail.
“M•BOX MAIL HIGHTLIGHTS
At last you can easily get your Hotmail on your iPhone. m•Box Mail is designed to help you get your Hotmail as you are used to getting your Hotmail. It is like the “native” or built-in mail application on the iPhone – only it speaks the Windows Live Hotmail protocol.
Finally, you can have your Hotmail messages and folders on your iPhone screen ready to use at a moment’s notice. No more trying to log onto a Web site and struggling through your email. Instead you can access your Hotmail, organize it, delete it and send it – all from your iPhone, with the familiar iPhone user interface you’ve become so adept at using.”