Hmm, that might be interesting. Send message to member list on every new post with option to manually send a message as well. Are you thinking each npub.pro user would add smtp email settings in app or a unified provider for all npub.pro users? Bulk DMs would be less popular because most website users probably don't have a nostr client, and those that do can already see new posts on their existing client, but like others said, probably easier to implement.