Email petitions do more harm than good.
Don't forward them, and for heaven's sake don't start them. Obviously, circulating a dead petition is just a waste of time. Read the Cautionary Tale article below to see what I mean. So when someone tries to return a completed petition, it just bounces because the address is dead, and all the signatures are wasted. You've probably seen petitions that say that you should mail it back to the author if you're the 100th, 200th, 300th etc.