Antispam blacklist lookups work by reversing an IP address and querying a DNS blacklist. You can test this manually:
Test in a CMD window
To test SpamCop blacklist:
ping 1.1.168.192.bl.spamcop.netThis should fail (no response) because 192.168.1.1 is a private address not on the blacklist.
ping 2.0.0.127.bl.spamcop.netThis should succeed and return 127.0.0.2 because 127.0.0.2 is a test address that is always listed.
If the first ping succeeds or the second ping fails, there is a DNS problem — typically extra domain suffixes being appended to queries. Fix your network adapter DNS suffix settings.