There is a good cure for e-mail SPAM – digital signatures. If lots of people (meaning most) do digitally sign their e-mails, then you can be sure of who is the sender and block anything that you don’t like. As digital signatures can be validated (by companies, as well as by any individual), you can reject any unknown signature, if it is nto signed by someone you trust, like a colleague validated that this signature belongs to the person/organization that claims its his/her.
Start the cycle, sign you own e-mail with PGP. Create a key (free), have it signed by colleagues, friends, etc. and publish it for validation.
