When a Blacklisted host connects to the SMTP module, the module does not reject a connection. Instead, it receives the MAIL FROM SMTP command, and starts to process the recipient (RCPT TO) addresses sent from the blacklisted host. The module adds the domain blacklisted to each recipient address received from a blacklisted host, i.e. the received address user@domain is converted into user%domain@blacklisted. Then the address is processed with the Router as usual. If the Router Table does not contain special rules for the blacklisted domain, the address is rejected with a special error code.
The default Router Table contains the following line: blacklist-admin*@blacklisted = postmaster All messages from blacklisted hosts sent to the blacklist-admin address in any domain, are routed to the postmaster, so these messages are accepted. This "white hole" feature allows the blacklisted host users to contact the postmaster on your server if they want to discuss the blacklisting issue. If you remove this line from the Router Table, no address will be accepted from blacklisted hosts.
When rejecting addresses sent from blacklisted hosts, the SMTP module verifies if the blacklist-admin@blacklisted address can be routed with the Router. If the Router Table contains such records (a default one or a different one), the error code sent back to the blacklisted host explains that mail to blacklist-admin@serverdomain name is accepted even from that blacklisted site.
If you want to provide a "white hole" feature, but you do not want the information about the white-hole address to be included into the error code, simply use a different name for the "white hole" address.
abuse*@blacklisted = postmaster
The following table contains samples of SMTP sessions established from a blacklisted host. The host commands are marked with C:, the SMTP module responses are marked with S:.