I disagree. I don't believe that would solve spam you would just force the spammers to use much more aggressive tactics. If you introduce a fee to email you're only hurting the people who actively communicate back and forth via email as a primary method. Mailing lists anyone?

Spammers will take your $0.02 fee per email as an operational expense. Most spam is not sent by the spammers themselves from their own servers but are instead relayed through a third party who handles the delivery part on their behalf who are paid money to run these spam campaigns through their servers instead anyways so they are already paying a fee, this is just an extra cost on top of what they are already paying to do it.