When you send an email with Overloop, we add a tiny invisible picture (a tracking picture) at the bottom of the email. When an email client (Gmail, Outlook, Thunderbird, etc.) opens the email, it will usually load the image. Loading this picture will make a call on our server, which allows us to log the open.
This technique is used in the whole email industry and is the only way to detect opens.
The issue is that some email clients don't display pictures automatically to protect privacy. They usually display a message asking if you want to display pictures or not. If the recipient does not click on "display pictures," we will not be able to track that the message has been opened.
How to ensure all my prospects' opens get tracked?
Unfortunately, there is no way to track 100% of opens accurately since it depends on the email client configuration (on the prospect's device).
That said, setting up your own tracking domain can increase the chances that the email client displays images automatically.
How come an open is tracked when I click on a link or open the email myself from my sent folder?
Because of the technique used to track opens, there is no way to know who opened your email. If you open your own emails (from your sent folder), then the tracking picture will be loaded, and we'll record an open.
To avoid missing up stats do not open your own emails.