All this is based on the wrong premises. The reason why spam is an issue with email is, anyone can send emails and it's not always possible to identify the sen

All this is based on the wrong premises. The reason why spam is an issue with email is, anyone can send emails and it's not always possible to identify the sender. Once encryption is deployed then the sender is associated with a public key and it's possible to establish a web of trust. Gmail could also manage identity-based scores based on all it's user's trusted connections.