Do they still send cards in the mail? It would be interesting to see if something they sent as an unrelated advertisement would be covered by your contract if y

Do they still send cards in the mail? It would be interesting to see if something they sent as an unrelated advertisement would be covered by your contract if you can prove they received the contract and the card was mailed after. This could be a whole new era of spam prevention, by being personally as full of it as every EULA. Just send out contracts, "by contacting me in any way you agree to the following...". Companies would be terrified to send anything at all to anyone.