1. There are (perhaps silly) reasons for newsletters to have tracking which is that if you send them to people who don’t read them then, even though it’s easy to unsubscribe, big mail hosts (eg Google) can down rank your host in their spam filters. Worse still, some users treat the spam button as “please delete this thing I am not interested in” but that is not really how the signal is interpreted by the mail host. The solution is for newsletters to auto-unsubscribe users if they seem to stop interacting with the emails.

2. The actual threat to the newsletter boom is that advertisers realise that, just like every other fad format before, newsletters aren’t a particularly better way to reach audiences, and so they will stop paying so much for the ad space. Or they will move on to some other fad format and demand will fall off a cliff.