the mail is rejected by the email servers of the ppl you send to? I find that not many email servers in the world use the RBL lists, so some mail should get thru at least.
You sure its not your own server thats blocking it? Remove the sites you have listed in the RBL entries and give it a go. I found that spamassassin was blocking my own mail going out if the sensitivity was higher than Medium, but also, by using different RBL list sites, you can find one that doesnt list your own IP address range that someone else abused before you got it...