How can an open be registered to my subscriber if they didn’t manually open my message?

When looking at open stats for your messages, you may see things like messages opened immediately upon the message being sent, or you may hear from your subscribers that they never opened a message.

The reason that this can happen is due to how open stats are tracked. These are registered by an invisible pixel in the HTML message loaded. This tracking pixel that is used can be triggered by both humans and machines.

• Gmail proxy opens
• Yahoo proxy opens
• Microsoft (hotmail/outlook) proxy opens
• MacOS and iOS proxy opens, both at delivery time and whenever you plugin your device to charge. Frequently at nighttime on your bedside table.
  • https://blog.aweber.com/email-marketing/apple-gathers-your-personal-data.htm
  • https://blog.aweber.com/email-deliverability/apple-ios15-open-rate-trends.htm
• Many other 3rd party filters and security appliances will register automated opens.

Due to these proxies, it's impossible to tell the difference between an automated open and a human open as most opens are proxied these days for privacy reasons.