MailEssentials supports Exchange, Lotus Notes, and other SMTP-based solutions, providing multi-engine spam filtering, anti-phishing protection, and business policy enforcement.
Using MailEssentials, an organization can manage spam in various ways. First, use of SpamRazor, as a supplement to the core engine, helps achieve the 98 percent blocking rate claimed by GFI.
Next, bayesian filtering provides zero-day protection from new spam. Inspecting outgoing mail, the filter learns which email sources are probably valid senders. If the capability is turned on, it can also learn about valid email by inspecting public folders into which users drag messages they've received. Senders can also be blocked in this way.
In addition to using public folders, MailEssentials provides blacklisting via a selection of third party services. A list is shown in the provider selection window below. Using frequently updated lists helps protect against receiving phishing and other email with malicious intent from reaching user mailboxes.

click to enlarge
Use of keywords is also supported for blacklisting incoming mail.
On the other end of the protection spectrum is whitelisting, supported in MailEssentials via IP addresses or domains. Although turned off by default, users can be notified when a "clean" message is received from a source not in the company whitelist.
MailEssentials also supports very basic message archiving, a very small subset of the powerful functionality found in GFI MailArchiver. The screen shot below shows the administrative interface which allows message search and restore capabilities. Unlike MailArchiver, only the administrator has access to archived messages.

click to enlarge
Finally, MailEssentials supports multiple user-defined policies. The administrator can prioritize the policies to achieve desired results.