Intelligent Message Filter is enabled on the mailbox server

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at]  

Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine whether Microsoft Exchange Intelligent Message Filter is installed and enabled on the server:

HKEY_LOCAL_MACHINE\ Software\Microsoft\Exchange\ContentFilter

The Exchange Server Analyzer reads the ContentFilterBindings value in the ContentFilter registry key to determine whether Intelligent Message Filter is installed and enabled on the server.

The Exchange Server Analyzer then queries the Active Directory® directory service to determine the value for msExchAuthenticationFlags attribute for the Exchange Server object. The msExchAuthenticationFlags attribute represents the type of authentication that is allowed on the server. The Exchange Server Analyzer displays a warning message if the following conditions exist:

  • Authentication on the msExchAuthenticationFlags attribute has been configured to allow anonymous access to the server.

  • The server also hosts mailboxes on it.

Intelligent Message Filter identifies messages that are likely to be unsolicited commercial e-mail (UCE). To filter UCE effectively, you must deploy Intelligent Message Filter on your Exchange gateway servers or Exchange bridgehead servers if you use non-Microsoft e-mail servers at the gateway. These gateway servers accept incoming Internet e-mail messages and forward these messages to the appropriate mailbox server. Generally, gateway servers do not host mailboxes.

Additionally, you must enable Intelligent Message Filter on each SMTP virtual server that accepts Internet e-mail messages on your Exchange gateway servers.


Do not disable anonymous access on your Internet gateway SMTP virtual servers. These SMTP virtual servers that accept mail from the Internet must allow anonymous access.

To filter UCE, you can configure Intelligent Message Filter by setting thresholds for the spam confidence level (SCL) ratings that are assigned to incoming messages on both the gateway and the Exchange mailbox stores. Intelligent Message Filter evaluates each incoming message and assigns the message an SCL rating that is based on the likelihood that the message is UCE. Exchange mailbox servers use the SCL threshold and settings that are specified for the mailbox store to determine whether to deliver a message to a user's Inbox or to a user's Junk E-mail folder.


Intelligent Message Filter does not have to be installed on Exchange mailbox servers. If Intelligent Message Filter is installed and enabled on the gateway SMTP virtual servers, Exchange mailbox servers receive the SCL rating with each incoming message and take the appropriate action.

For information, see the Exchange Intelligent Message Filter Web site ( For more information about configuring your Microsoft Exchange Server 2003 organization to send and receive Internet mail, see Exchange Server 2003 Transport and Routing Guide (