Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine the value for MaxMessageCount:

HKEY_LOCAL_MACHINE\Software\TrendMicro\ScanMail for Exchange\CurrentVersion

In addition, the Exchange Server Analyzer also queries the Active Directory® directory service to determine the count of the entries listed in the homeMDBBL attribute of each mailbox store. The count of this attribute represents the number of mailboxes on the mailbox store.

If the Exchange Server Analyzer determines that the Exchange Server contains more than 100 mailboxes, and that the value for MaxMessageCount is less than 500, a warning is displayed.

Trend Micro ScanMail for Microsoft Exchange provides antivirus protection for Exchange Server. After ScanMail for Exchange scanning thread finishes a task, it writes the scanning results to a queue. If there are too many items in that queue, the scanning thread must wait before it can write to the queue and release the thread. The threshold of the scanning result queue size is controlled by MaxMessageCount. Setting the MaxMessageCount value to 500 optimizes performance for ScanMail for Exchange.

This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To correct this warning

  1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

  2. Navigate to: HKLM\Software\TrendMicro\ScanMail for Exchange\CurrentVersion

  3. In the right pane, double-click MaxMessageCount.

  4. Enter a value of 500 (decimal).

  5. Close the registry editor, and then restart the ScanMail_RealTimeScan service and the Microsoft Exchange Information Store service for the change to take effect.

Before you edit the registry, and for information about how to edit the registry, read the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows registry" (

For more information about using the MaxMessageCount registry value, see the Trend Micro Web site (

Web addresses can change, so you might be unable to connect to the Web site or sites mentioned here.

For more information about fortifying an Exchange environment against e-mail transmitted viruses and worms, see "Slowing and Stopping E-Mail Viruses in an Exchange Server 2003 Environment" (

For more information about using antivirus software with Exchange Server, see the following Microsoft Knowledge Base articles:

For a list of third-party antivirus software that is available for Exchange Server, see the Exchange Server Partners: Antivirus Web site (