DNS blacklists are databases of known spammers that are maintained by various organizations on the web. One of the most popular is the list of open relay servers maintained by ORDB.org, the Open Relay Database. Almost all spam received by users comes from a common source mail servers that are not properly secured, those that allow mail to be relayed through them. To account for this, GFI MailEssentials can be configured to query the ORDB or other such databases, and to either allow or deny mail from these sources. While querying DNS blacklists will slow down the message reception process somewhat, it is a highly effective tool, especially when used in conjunction with the MailEssentials whitelist feature. When messages are blocked by a blacklist, you have the option of automatically deleting them, moving them to a designated folder, or forwarding them to another address (such as an Exchange public folder!) for later review. Both the blacklist and whitelist features of GFI MailEssentials 8 are included in the freeware version of the product.
As if spam werent annoying enough, youve probably noticed that you receive an awful lot in other languages, especially in the kanji character set. To account for this, GFI GFI MailEssentials 8 also allows you to block messages by language, ensuring that those messages never reach end users.
One of my favorite anti-spam features of GFI MailEssentials 8 is one that you might easily overlook, but is one that should not be underestimated. The product is capable of delivering fake Non-Delivery Reports (NDRs) to any addresses associated with your blacklists. But why would you want to do this? The reason is simple almost all spam is automated by software, and in order to keep their lists clean, most spamming software is configured to automatically remove addresses from its list for which it receives an NDR. Sure, it may not be honest or truthful, but then fighting spam is a dirty business!