Thanks jym626 for your last post and you are absolutely correct that the problem is made worse if any CC user marks these emails as spam.
I will discuss the notification with Roger and Lenitus and let them handle it as they see fit. Good idea and thanks for suggesting it.
I will make an inquiry of our email delivery provider if they have had any response from the ISPs that are blocking our email. Since the resolution at this time rests in the hands of external ISPs, there is little we can do but be the squeaky wheel and wait.