dcc: distributed checksum clearinghouse (antispam tool)
dcc: 
dcc: The DCC or Distributed Checksum Clearinghouse is an anti-spam content
dcc: filter that runs on a variety of operating systems. As of mid-2006, it
dcc: involves millions of users, tens of thousands of clients and more than
dcc: 250 servers collecting and counting checksums related to more than 300
dcc: million mail messages on week days. The counts can be used by SMTP
dcc: servers and mail user agents to detect and reject or filter spam or
dcc: unsolicited bulk mail. DCC servers exchange or "flood" common checksums.
dcc: The checksums include values that are constant across common variations
dcc: in bulk messages, including "personalizations."