Maybe a new system could instigate whitelisting from the ground up, with a built in "contact request" protocol (which may be required anyway to exchange keys).

Maybe a new system could instigate whitelisting from the ground up, with a built in "contact request" protocol (which may be required anyway to exchange keys). We've got very used to email's totally open mailboxes, and it seems to me that the cost may well outweigh the benefit. Edit: Added comment about key exchange.