The authenticated newsletter is a small added value, but it is a detail nobody else has. Anyone who signs up gives two confirmations and is recorded on a blockchain. We certify the date and time of the sign-up. What does that mean? For one thing, in case of theft by a disloyal partner.
They would have to prove that they collected that data themselves. The server that sends the newsletter records every operation with a timestamp: anyone who wants to challenge it needs one too, and that is much harder to prove. And if there are two, which server is right? There is a whole series of recognition issues that rule out any confusion. Organised this way, the list becomes an asset: built with two opt-ins and a timestamp, it has economic value.