I am study computer science and have a final project at the university on the subject of emails and clients. The project we are working on is to create a dashboard that allows the user to send an email through us and receive indications of the email - viewing the email, displaying the responses to the email from recipients and more..
One of the features we need to support is knowing who has read the email to the user. When it comes to sending an email to one recipient we were able to solve it relatively easily according to what we found on the internet - we planted a 1x1 pixel that makes an api call to our server and reports that the email was read and it worked! We need to support this feature even when the user sends an email to 4 different recipients. To know which of the recipients read the email. We saw on the Internet that this feature exists in many products, but we could not figure out how to implement it. Any idea or direction how to achieve this?
I have searched online for solutions and reviewed many products to see this is possible.