mail/dcc 2.3.169 OpenBSD

The Distributed Checksum Clearinghouses or DCC is an anti-spam content filter that runs on a variety of operating systems. The counts can be used by SMTP servers and mail user agents to detect and reject or filter spam or unsolicited bulk mail. DCC servers exchange or "flood" common checksums. The checksums include values that are constant across common variations in bulk messages, including "personalizations."

The DCC software is distributed under a license that is free only to organizations that participate in the global DCC network. ISPs that use DCC to filter mail for their own users are intended to be covered by the license. You can redistribute unchanged copies of the DCC source, but you may not redistribute modified, "fixed," or "improved" versions of the source or binaries. You also can't call it your own or blame anyone for the results of using it.

Organizations selling anti-spam appliances or managed mail services are not eligible for the free license.

The DCC client programs are configured to use the public DCC servers by default. You should use these if your mail system handles fewer than 100,000 messages per day. If your system handles more than that, you should run your own local DCC servers as part of the global network.