Working in the SAME SPREADSHEET
I do not know if you have this function.
You can choose to reply after the initial mail with people that had opened your mail and the others that had not opened your mail with all in the same spreadsheet.
It would be good if all is in the same spreadsheet. As of now, I got to duplicate the same spreadsheet and then send out 2 different mails with one that had opened, while the other that had not opened.