m-p{3}

At the moment you can’t. The only realistic way I could see that happening is if the servers would check the app’s digital signature and refuse the app from communicating with the official infrastructure if it didn’t match.

I personally hate newsletters because

1. my email inbox is already cluttered enough as it is
2. I need to share my email to subscribe, which puts the balance of power into the hands of the sender at the expense of my privacy

I’d rather have newsletters made available through RSS feeds, where I can subscribe and unsubscribe anonymously.