Overview of the Whitelist/Blacklist Mechanism

Postfix recieves an inbound connection from a client (MTA, mail client, etc) This client gives postfix this information when requesting access to deliver mail:

• Source email address
• IP address of the connecting client
• Destination Address

If SQLWhite is installed and running, Postfix will hand off this data to SQLWhite and expect one of three answers:

• "OK"- Unconditionally accept this email (bypassing other spam filters and mechanisms)
• "REJECT"- Reject the mail
• "DUNNO"- Cannot make a desision (send the mail along to other spam filters)

SQLWhite decides on how to handle each email by taking the information given by Postfix and comparing it to a database looking for matches, and replies according to the most specific match. The fact that the most specific match is chosen is important. If there is no match, SQLWhite will tell Postfix "DUNNO", and the mail will go through the rest of the validation mechanism.