This list is maintained by Thoroquel Systems LLC from Columbus, Ohio. The list has been initially created for their personal use but now is in public beta. They do not recommend using it directly to block connections.
XPEWS is a *PEWS style list. Therefore you should expect whole blocks to be listed.
Delisting is possible if you meet their critaria. The list of things to be carefull during requests is listed on their website.
Is the information on our site wrong or incomplete? You don't want us to monitor your blacklist? Or do you operate a similar blacklist? We would like to hear from you!
We keep some statistics on blacklists. Below is the graph for xpews.mailhosts.org. We test blacklists by asking them to respond to known IP's that are blacklisted and known IP's that can't be blacklisted. Not every blacklist has such IP's, we test them with what is possible. We keep if we get any response or error messages and the response duration. Lower response times are better. These statistics may be useful for email server administrators to pick which blacklist to use.