I'm fed up by spam and would like to have an email address that will only deliver mails signed by users I declared trusted. Some kind of purgatory for mails the signatures of which are trustworthy by a Web of Trust connection would of course also be a nice feature. Is there a either provider that offers this service, or at least a (preferably FOSS) mail server setup for self-hosting?
We are currently in development of this functionality as a Cloud Application that will run in your private cloud on the Jumpto.com Internet Security platform. Secure Mail will eradicate spam by making your email address unresolvable on the normal Internet by unauthorized users. More information on the product will be released upon roll out in the next few weeks.