[jonifen]

I'd recommend (if using Outlook) to look into the email properties and check the MIME headers of the email - may give an idea as to where the email originated from and action could be taken from there.
It may be worth looking into using a program like Mailwasher to fire emails back where they came from for a few weeks - see if this helps reduce the amount of spam emails received. It may actually help (it has done for me in the past).