Allan,

That sort of thing is getting pretty common these days. Archies, and a few other ISP's were rejecting email from me as spam for a while, on and off.

What happens is that some of these ISP's subscribe to one or more lists compiled by companies that track spammers and the mail servers that spam originates from. They then simply refuse to accept any email that comes from that ISP's mail server. This forces the operator of the mail server, (your isp), to crackdown on spam originating from their customers. When they do, they then can contact those companies that create the blacklists, and they can get their mailservers removed from the list and all will work again.

You should complain to your isp and they will get the problem fixed, usually within a day or two.

Greg