Agressive email filtering?

Over the years I have made many friends on line. Some write to tell me their stories or to catch up with where others are. In that time contacts have been made with people world wide. Some, however have misused the email service by sending large numbers of useless messages to as many people as possible. Let's refer to them as the world of S-P-A-M. We have all had some annoyance from this practice and the misuse of legitimate services. In one case my own link page scripts were misused by people who submitted links and entered other people's email addresses with them I got blamed when their activity caused unwelcome mail from my services.


Now I have found there is a legacy that is causing a new problem for genuine users. A certain ISP (legitimate) in its attempt to prevent such problems has labeled several internet service providers in my country as sources of such mail. So instead of blocking the email addresses involved, they have blocked all mail that comes from those services.

I have just been informed that although my messages resulted in rejection errors, the intended recipients got their mail. This would surely require a weird set of circumstances involving malfunctions in the ISP systems.

As a result of this, thousands of innocent people believe they are being cut off from emailing friends who use those services just because somebody else did something bad, or because of a system error and these innocents may be punished for the wrong doing of others.

What would you think if your ISP behaved like this?