Bananatag uses similar technology as mass-email marketing companies to track email opens. This is achieved by inserting a small and transparent image (or Tracking Pixel) into the message being tracked. When the email is viewed by your recipient (and the image is downloaded) an Open is recorded.
Some important considerations about Opens:
If the person opening the message has images disabled you will not get an open notification. This may be set to default in some email programs due to abuse by spammers.
Sending an email to yourself and opening it in the same browser will not trigger an Open. When you track an email, Bananatag sets a cookie so that you don't receive Opens from yourself (when going through sent items for example). When Testing Opens, it's best to open from a different device than the one you track from.
If the recipient uses plain text email you will not get an open notification. While the vast majority of people do not use plain text email (and will automatically download your tracking pixel) it's important to remember this may not always be the case.
Some email programs may re-download the content of a tracked email multiple times while the message is open. While we have systems to minimize instances where multiple open notifications are sent for the same tracked email, this is also possible.
Since there are some instances where it won't be possible to determine if an email has been opened, it's important to remember that your open rates will be as good or better than what is displayed in your account. Additionally, the considerations above have no impact on how links are tracked.