Allow contract owners to specify newsletter sender address in contract which be able to send email to contract members (for ERC20 it would be token owners, for other types of contracts it could be specified list of addresses etc.) and set sender address to this contract.
Sending newsletter: Special address specified in eg. ERC-20 contract would send one email to contractAddress@ethmail.cc and this email would be distributed to all current owners of given ERC-20 token
This could be extended into more general functionality.