Block Botnet Spam

There are some systems on the Internet that attempt to track the TCP/IP addresses that ISPs assign to consumer PCs. These lists are published in DNSbl format. It is common to refuse all E-mail sent directly from known end-user sources. Users on these connections are supposed to use their ISPs E-mail servers for relaying. Anyone sending mail directly from one of these connections is very likely (99.99%) to be a spammer.

You can use the following DNSbl to stop Botnet and other Direct to MX spam:

On a more restrictive server you may also choose to block all connections from systems with no reverse DNS or reverse DNS that is obviously generic (ie. contains a modified IP address). Doing this will eliminate the majority of Botnet with very little overhead.

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