forwarding emails

Do you forward a lot of emails? I do receive a lot of forwarded emails though I hardly forward any as I do rarely and only those that I feel are really important and of interest to the receiver. Receiving forwarded emails in bulk are a real problem but I cannot even block the sender as it happens to be friends - what to do in a situation like this? as telling them not to send does not help either - this has become their habit of forwarding everything, jokes, pictures, pp presentation, news articles, family pictures, .....etc!!!