A number of MailEssentials Anti-Spam filters which include IP Blocklist, Directory Harvesting, and the IP DNS Blocklist filters can be configured to execute when the full email is received or at SMTP Transmission level. In SMTP Transmission filtering, 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, economizing on 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.
Important: To make the best of SMTP Transmission filtering, use it when MailEssentials is installed on an Internet gateway or when it is the first server to receive emails from the Internet.
The next section provides the procedure to configure the various SMTP Transmission Filtering properties.
- Navigate to Anti-Spam > Filter Priority and select the SMTP Transmission Filtering tab.
- Click Switch to toggle the Directory Harvesting filtering between:
|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.
Note: The Greylist filter runs at SMTP Transmission level only.
- Click Apply.