I have the same problem If I am sending mail to some. I get the mesage that I am on a blacklist. It's a whole range of ip adresses from my isp.
Going to try to get un listed.
But for that to happen going to use my isp smtp server. I have some questions thoug.
1 must I use smtp.myispdomain.nl or must I use the server, that I also have setup in outlook like netmail.myisp.nl?
And if I send with my isp server witch mail address will the receiver see?
The one I made in ISPConfig or the One I have with my ISP?
Updating my server to Debian Squeeze, so here I go again...