someone elses profile picture showing when i send emails?

Can anyone help I really don't know where this is coming from? A friend asked why I had some stranger as my profile pic on my emails.  He had seen the picture for the last 3 weeks but just thought to mention it. I have checked my facebook, twitter photos etc and email addresses linked and they are ok. Is it possible that someone somewhere has typed in MY hotmail address and their picture is LINKED to me. It is of concern as the photo is of bad taste and I cannot get rid of it!!