This article aims to explain how to configure the IP Blocklist, Directory Harvesting, and the IP DNS Blocklist filters to run either at SMTP level or at Full Email level.
The IP Blocklist, Directory Harvesting, and the IP DNS Blocklist filters can be configured to execute either when the full email is received or at the SMTP Transmission level. When these filters are configured to run at SMTP Transmission level, emails are scanned whilst they are being received.
SMTP level filtering terminates the email's connection and therefore stops the download of the full email, saving bandwidth, and processing resources. In this case, the connection is terminated immediately and emails are not required to go through any other anti-spam filters. This will also prevent emails from being quarantined, making it impossible to approve or release them later.
To make the best of SMTP Transmission filtering, use it when GFI MailEssentials is installed on an Internet gateway or when it is the first server to receive emails from the Internet.
The following steps provide the procedure to configure the various SMTP Transmission Filtering properties:
- Open the GFI MailEssentials UI.
Navigate to Anti-Spam > Filter Priority and select the SMTP Transmission Filtering tab.
- In the Optional SMTP filters list, click on the Switch button for either of the available filters to toggle between the following modes:
Filtering Mode Description Filtering on receiving full email Filtering is done when the whole email is received. Filtering during SMTP transmission
Filtering is done during SMTP transmission.
If this option is chosen, the filter is always run before the other spam filters.
- Click Apply.
- Optional: Configure the actions for the desired filter if it's running in Full Email mode, by following the steps in the "Configuring MailEssentials Spam Actions" article.
The Greylist filter runs at the SMTP Transmission level only.