Have you ever managed a newsletter? Mail providers such as gmail use things like open rates to determine if a message should be in important, promotions, or spam.

Also, a sizeable chunk of people refuse to click unsubscribe links and instead hit the spam button. This can be a sensible response, as a lot of spam senders ignore unsubscribe. But it is also hard for legit newsletters.

So what is the best practice? Pruning your list of people who never open it. This improves open rates, makes gmail like you, and unsubscribes people who already would prefer not to read your letter.

Now it will be much harder to know who is inactive so you’ll end up sending more mail to people who don’t want it. And no double opt in doesn’t solve this.

There are other ways around the problem, but you seem to be in complete ignorance of what newsletter senders use tracking for.

Open rates also let you diagnose deliverability issues.