Hotmail sending problems???

i am on mac and use iMail for email client, and a macbook air, also an Iphone...

if i log into hotmail though safari i can send email fine - been testing this...

or boot into windows and use windows live mail....

if i try send an email through iMail on mac or iPhone it fails!!!

'cannot send message using the server smtp.live.com'

i then test the smtp and the pop servers and i can log in fine...

so what gives... very much need to be able to use my hotmail...