Well, if it was in URIBL/SURBL, you couldn't use it to post samples to this mail list, which is kinda the purpose, isn't it?
then dont provide urls. use numbers like dating agents. "i posted my sample on the sa spambin. id 213912" -> reader checks spambin.apache.org which has nothing but a field to enter the id and a warning message -> enters the number -> reads the spam sample with highlights and all the candy.