Wow, when did this become a thing? My not-very-bright Big Brother, Verizon, decided that my email responding to a friend was spam, and will not let me send it. It was, in fact, an explanation for how to detect phishing email. Thanks for helping to make the internet more secure, Verizon. So now I have to send email to some stupid address and maybe some day you'll let me actually communicate legitimate non-spam information on this service for which I pay you a substantial sum? What other recourse does a customer have when Verizon's incompetence and indifference to customer service interferes with my use of the services that I've paid for?
tl; dr: Verizon screwed up by marking outgoing email as spam when it isn't. How do I fix this and who do I complain to?