Unwanted, unpleasant emails

I keep getting unwanted emails that are to be honest not very pleasant.  I've never knowingly ever visited an adult site, if you understand what I mean by adult, but I get emails offering me contact with women, medicines to aid my sexual prowess. I get these emails several times a day.  I have made sure all that I receive go straight to my junk mail folder, but is there anyway i can stop receiving them altogether.  As I said I'm completely new to forums and am extremely embarrassed by having to contact people this way but my seven year old granddaughter, who was using my desktop the other day to email a friend accidentally opened a particularly horrid one  that she thought was a reply for her.  Please can you advise me.

Regards  Steve