So you registered the account recently, and when you did you somehow "supplanted" the existing account? Or have you had the account for a while and suddenly started getting this guy's mail?
As others have stated the problem is that someone thinks their address is saiganesh@gmail.com when it really isn't but they use it anyway.
If you can find another way to contact this other person you might try it to tell him that his email is not what he thinks it is.