Users complaining of SPAM

Hi ~ I administer/supervise a network for a public school district. I have tried to explain to users (’til I’m blue in the face) that SPAM happens. Aside from warning them about distibuting their e-mail address etc., etc., they continue to be inundated with SPAM and PHISH attacks (like myself!). What are some responses that have been used with computer/e-mail users (without being too harsh) to get people off of one’s back!?

Thanks
Tim