Read receipt. Gmail offers it only in Google Workspace accounts; Outlook offers it in many versions. The recipient can refuse, and many programs never send one.
Tracking image and link. A tool such as HawkOpen adds an invisible image and redirected links; HawkOpen does so only after your company switched tracking on, and only for recipients whose consent is recorded. You see when they were loaded or clicked, but Apple Mail, Gmail’s image proxy and company scanners also do that without a person. HawkOpen labels these events, and events classified as a machine never fire an alert; a single open or click does not send a notification, while replies do.
What to do: send through HawkOpen, look at opens and clicks classified as likely human activity, and treat a reply as the only certain answer. If the answer matters, simply ask the recipient to confirm.