Dennis, what happens is when a lot of spam gets reported from a certain ISP (in your case netptc.net) the other ISP's can often reject any mail from that ISP as a way to force the ISP to take action and clean up their house. Some ISP's don't give a rip about spam as long as the customers pay, but when they start getting complaints about email getting rejected, then they take action and kick the spammers off their network.

Not saying that's what is happening for sure, but I have seen that happen before.

Also, in your email to these people, does it have a link at the bottom, how AOL puts that ad on the bottom? Some email systems will reject as spam if there is a link that does not match the sender's ISP.

Dave.