What is the Distributed Checksum Clearinghouse or DCC?
The DCC or Distributed Checksum Clearinghouse is an anti-spam content filter that runs on a variety of operating systems. The idea of the DCC is that if mail recipients could compare the mail they receive, they could recognize unsolicited bulk mail. A DCC server totals reports of “fuzzy” checksums of messages from clients and answers queries about the total counts for checksums of mail messages. See the main DCC man page as well as the DCC web page and its mirror.