This is also what we do with bitmaelum[1]. Each message needs a proof of work for deliverance. Large (authentic) mailinglists can use an opt-in by a reader whic

This is also what we do with bitmaelum[1]. Each message needs a proof of work for deliverance. Large (authentic) mailinglists can use an opt-in by a reader which allows the sender to bypass the pow restriction. [1] https://github.com/bitmaelum https://github.com/bitmaelum