someone has hacked into my inbox and sent out emails in my name.
 

I discovered this when I received mail delivery failure notices. why was security breeched in my hotmail inbox? The email that was sent out was advertising cheap viagra med. that could be ordered on line. Friends notified me that they received this email and were offended by it. So why or how did someone get into my inbox and get a hold of my list of contacts and then were able to send out this email.