Delisting
According to the SPEWS FAQ, listings were removed when the spam or spam-support has stopped. Just as they did not solicit nominations for listings, the SPEWS operators did not solicit requests for delistings. There was no contact information published on the SPEWS Web site. There was no spews.org mail server, and the operators of SPEWS did not receive email under the SPEWS name.
It is believed that the operators read certain Usenet newsgroups related to spam and email abuse. However, no poster has claimed to be a SPEWS operator and no regular of the newsgroups claims to know their identity. By the accounts of many of those regulars, SPEWS can detect automatically when such support stops, but this was not supported by any information in the SPEWS FAQ.
Read more about this topic: Spam Prevention Early Warning System