Note: the following tech-letter is specifically for Gmail, though there are surely similar options for other mail clients out there.
In most online-cases, I tend to opt-out of "read receipts" because I don't care to know if people have read my messages or not - it's unnecessary social anxiety for me. That being said... I can't say the same for emails.
I love emails (if you haven't already noticed), and since email communication isn't always instant, I like to know when people receive my emails, and if they were opened or not. You'd be surprised to know how many people ignore your emails altogether, or open it immediately and answer you several hours later (me).
Mailtrack is a free (with premium options) Google Chrome (or Brave) extension that does this for you. Once you add this extension to your browser and link it to your Gmail account, you can choose to have it inform you a whole lot of things.
First thing's first, add this extension to your browser and link it to your Gmail account, like in the image below.