Spam Filter detects the email sender’s reputation score. The reputation scores range from -10 (bad) to +10 (good). An email is classified as spam if the sender’s reputation is below the spam threshold, or is classified as suspected spam if the sender’s reputation is between the spam threshold and suspected spam threshold. An email is not classified as spam if the sender’s reputation is above the suspected spam threshold.
Spam Filter detects spam emails based on the reputation score of the sender’s IP address. The sender’s address is the address of the host that connects to the SMTP server to deliver an email message, not an address within the email header.
1. Click Security Services > Spam Filter.
2. Click On to enable Spam Filter, or check Off to disable it.
3. If you enable Spam Filter, enter the following information:
• SMTP Server Address/Domain: Enter the IP address or domain name of your internal SMTP server. The SMTP server must have its Internet traffic routed through the security appliance. The SMTP server or the clients that use this SMTP server can be configured to respond to the spam and suspected spam tags that the security appliance applies to the email.
• Action when Spam Detected: Choose Block Email to block the email, or choose Tag Email with [Spam] to get the email tagged with [Spam].
• Action when Suspect Spam Detected: Choose Block Email to block the email, or choose Tag Email with [Suspect Spam] to get the email tagged with [Suspect Spam].
• Reputation Threshold: Specify the block sensitivity as Low, Medium, or High, or as a numerical threshold (Custom).
– Low: Blocks less spam with lowest risk of false positives. The threshold value for spam is -4 and the threshold value for suspected spam is -2.
– Medium: Blocks more spam with moderate risk of false positives. The threshold value for spam is -3 and the threshold value for suspected spam is -1.
– High: Blocks most spam with increased risk of false positives. The threshold value for spam is -2 and the threshold value for suspected spam is -0.5.
– Custom: Manually set the spam reputation threshold. When the Custom radio button is selected, choose the threshold values for spam and suspected spam. The allowable values for the threshold are integers from -10 to -1 and the value -0.5.
4. In the Allowed Senders area, you can specify the email sender exceptions against your Spam Filter settings. Traffic from the specified hostnames or IP addresses will not be examined by Spam Filter.
• To add an exception, enter the hostname or IP address of the sender in the Hostname/IP Address field and click Add.
• To remove an exception, select it from the list of Allowed Senders and click Remove.
5. In the Service Outage area, choose one of the following actions when Spam Filter is unavailable:
• Do Not Accept Emails when spam reputation services are not available: All emails are delayed until Spam Filter is available.
• Accept Emails even when spam reputation services are not available: All emails are delivered without checking for spam.