Part of the spam score for an email message is calculated using the IP address of the server that the message was received from. If an email forwarding service is used, the IP address of the forwarding server is used to calculate the spam score. Because the forwarding server is not the initial source email server, the spam score can be inaccurate.
To improve spam scoring accuracy, you can enter one or more host names or domain names of email servers that you trust to forward email to your email server. If you use SMTP, enter one or more host names or domain names for SMTP email servers that you trust to forward messages to your email server. If you use POP3, enter domain names for known or commonly used POP3 providers that you trust to download messages from.
After you add one or more trusted email forwarders, spamBlocker ignores the trusted email forwarder in email message headers. The spam score is calculated using the IP address of the source email server.