The PBL (Policy Block List) includes ranges of addresses that shouldn't be sending mail directly, either because they're retail customers who are supposed to use their providers' mail servers, or they're assigned to equipment that should send no mail at all. Each entry is a range of addresses. List maintenance is manual; network managers can and often do add ranges of their own addresses, and Spamhaus adds ranges that they've determined are appropriate. In some cases, it's possible to de-list an individual address to poke a hole in a PBL range and allow mail out.

The SBL is managed manually, and lists ranges of IP addresses that based on historical evidence are likely to send predominantly or entirely spam. Some SBL entries are single IP addresses, while others list entire networks that are controlled by criminals.

The XBL lists individual IP addresses of hosts that have been observed sending 'bot spam or other mechanical indications that they are likely to send spam but no legitimate mail. Listings are added automatically, and are removed automatically some time after the IP stops sending spam. It's usually possible to remove an entry manually, although not an unlimited number of times.