Walter,
I'm getting this: eval failed: available_nameservers: No DNS servers available! I do have nameservers available, and Net::DNS is installed, so I'm a bit stuck.
Is the file /etc/resolv.conf readable by user running spamd? Does it contain valid 'nameserver' entries? Running spamd (or amavisd) in a chroot jail? Are you using a directive dns_server or clear_dns_servers in your .cf file check its validity. Mark