Why do we see a sudden increase in our email opens?

Apple's Mail Privacy Protection (MPP) has changed the way that Insider receives opens and open rate data on emails as MPP pre-fetches and caches messages including the images in an email regardless of whether the intended recipient has opened the email.

That's why you might see increases in total opens and open rates of your email campaigns up to 2-3 times after Apple's introduction of MPP.