In Comcast's webmail you can try using a feature called "Read receipts". To request a Read receipt in Appsuite, click Options in the Compose window, then "Request read receipt".
Many third party email programs and apps also support Read receipts, but . . .
Read receipts only work if both the sending and the receiving email software support them (many webmail systems don't), and typically only if the recipient grants permission to send them (many users, like me, never do). Given the limitations, consider including some version of "Please reply so I know you got this" with the message you send.
My problem is that my emails are being sent out with return receipt requested whether I want that or not. This just started happening after a recent Comcast revision of the user interface. If I select Options and make sure Request Return Receipt is unchecked, my emails still go out with a return receipt request.