I have a Windows Live Mail hotmail account which I use on my pc, ipad and iphone.   I have been able to successfully send messages from my hotmail account on all three devices until today.  Now I get the following message every time I send an email to any account, including those that I have used frequently in the past.  I can send via another account from my pc but not my iphone when I'm on the move and need to resolve this issue as a matter or urgency.