To make SpamAssassin use DCC, uncomment the following line in the v310.pre file so the plugin gets loaded:
It is recommended to set explicit configuration in your "local.cf", so things are not relying on PATH etc.
I've installed DCC but I never seem to get DCC hits, even though I should. Why?
If you have installed DCC, and are running spamassassin or spamd without the "-L" switch, you should be seeing hits in spam reports.
Check your firewall setup. DCC uses UDP packets when replying, which are blocked by most firewalls by default. As a result, it requires that you open your firewall for DCC reply packets on UDP port 6277. Modern firewalls already track connections and replies, so simply having a standard rule like "iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT" is enough. For more information see: https://www.dcc-servers.net/dcc/FAQ.html#firewall-ports
If you're running a large site, processing upwards of tens of thousands of messages a day, the DCC maintainers have requested that you consider setting up your own DCC server as described in dccd(8), and arrange to peer with the rest of the public servers, to reduce their load.
Very detailed instructions on configuring DCC for a personal Unix account are in SingleUserUnixInstall.