If you prefer not to use Gmail as a middleman, these tools offered native Yahoo integration or desktop client support in 2021: : Offers advanced tracking specifically designed for the Yahoo Mail interface , including "invisible" tracking pixels [5]. Mailspring
If you'd like, I can suggest that are known to work with Yahoo in 2021.
: Just like WhatsApp, a single checkmark means the email was sent, and two green checkmarks appear when the recipient opens it.