The DCC maintainers have been in touch, noting that several sites seem to have set up SpamAssassin and DCC, but have not modified their firewalls to allow DCC traffic through! This is wasting their bandwidth, and we'd appreciate if users could check their configuration.
To check it, run 'cdcc info':
cdcc info
The output should contain lines like this:
dcc1.dcc-servers.net,- RTT+0 ms anon
dcc2.dcc-servers.net,- RTT+0 ms anon
...
There should be *at least one*, preferably more than half a dozen, of the public DCC servers listed. If this is not the case, a likely cause is an interfering firewall (see below).
Also note that DCC requires that you open your firewall for DCC reply packets on UDP port 6277. Here's sample firewall rules required:
allow udp local gt 1023 to remote 6277
allow udp remote 6277 to local gt 1023
Also, 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.