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,...) opens the email, it will usually load the image. Loading this picture will make a call on our server and this 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 in order to protect privacy, some email clients don't display pictures automatically. 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 contacts' opens get tracked?
Unfortunately, there is no way to track 100% of opens accurately since it depends on the email client configuration (on the contact's device).
That being said, you can increase the chances that the email client display images automatically by setting up your own tracking domain.
How come an open is tracked when I myself click on a link/open the email in 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 the 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.