email users that sign up for a sevice that I offer. I must approve each signup and the program uses the sendmail feature to email each person their password.
One account did not recieve thier email and I got a email undeliverable email from SquirrelMail in Cpanel with the following link.
http://www.spamcop.net/bl.shtml?209.152.178.152
The email said that my mail server was guilty of spamming and was blocked by them.
I can't post the entire email I recieved as it has personal info in it but if this is not enough info for now, I can submit it in a support ticket with all of the info. It is just that the forum is usally easier to get help from others here.