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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.

IPTables Setup:

Assuming you allow all outbound packets out of your machine, you only need to add an INPUT rule to your /etc/sysconfig/iptables file. Add the following line in your INPUT chain, above any REJECT rules:

-A <chain-name> -p udp -m udp --sport 6277 -j ACCEPT

DCC does not give hits in spamd

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