What email tracking does, and what it does not
Email tracking records two things: that a message you sent appears to have been opened, and that a link inside it was clicked. Both land on the contact and the deal, next to the calls, notes and messages already there. Used well, it answers a question every seller has after sending a proposal, which is whether anybody has looked at it yet.
It is equally important to say what it does not do. It does not tell you the customer read the document, understood it, or liked it. It does not tell you they are ready to buy. Opens in particular are an inference drawn from an image loading, and modern mail apps break that inference in both directions. Sales teams that treat opens as proof end up calling the wrong people confidently, which is worse than calling them uncertainly.