E-mail petitions are NOT acceptable to Congress or any other municipality. To be acceptable, petitions must have a signed signature and full address. Almost all e-mails that ask you to add your name and forward on to others are similar to that mass letter years ago that asked people to send business cards to the little kid in Florida who wanted to break the Guinness Book of Records for the most cards.
All it was, and all this type of e-mail is, is to get names and "cookie" tracking info for telemarketers and spammers to validate active e-mail accounts for their own purposes. Any time you see an e-mail that says forward this on to "10" of your friends, sign this petition, or you'll get good luck, or what ever, it has either an e-mail tracker program attached that tracks the cookies and e-mails of those folks you forward to, or the host sender is getting a copy. Each time it gets forwarded, then the origination is able to get lists of "active" e-mails to use in spam e-mails, or sell to others that do. (If you have been sending out the above kinds of email, now you know why you get so much spam!)
More on E-petitions at Snopes.