This is a server based error message and the mail server is doing filtering. Most likely you are relaying with a different email address than your ISP allows.
The solution most likely is that you need to use AUthenticated emailing where you log into the SMTP server. You can use the cUsername and cPassword properties of wwIPStuff to do this.
There's also more info on this issue here:
http://www.west-wind.com/wiki/kb.wiki?wc~EmailRelayingDenied+++ Rick ---
>Hi everybody!
>
>There´s a trouble trying to send mail. A friend of mine had a little system for the news. The system took mail addresses from a little table, then try to send it. If I try to send to mail addreses of the same domain there´s no problem, troubles start when I try to send to a diferent domain like hotmail, yahoo, etc., then appears the message:
>
>553 sorry, that domain isn´t in my list of allowed rcphosts (#5.7.1)
>
>Any ideas??? Thanks in Advance!!