Forefront Reverse DNS Lookup is Enabled
Topic Last Modified: 2008-01-14
The Microsoft Exchange Server Analyzer Tool looks for the following registry paths to determine whether the Forefront Antigen ReverseDNSLookup registry key exists and is set to a value other than 0.
On a computer with a 32-bit operating system:
HKEY_LOCAL_MACHINE \Software\Microsoft\Forefront Server Security\Exchange Server
On a computer with a 64-bit operating system:
HKEY_LOCAL_MACHINE \Software \Wow6432Node\Microsoft\Forefront Server Security\Exchange Server
A value other than 0 for the ReverseDNSLookup registry key means that the Antigen Perform Reverse DNS Lookup setting is enabled.
If the Exchange Server Analyzer determines that the Antigen Perform Reverse DNS Lookup setting is enabled, the Exchange Server Analyzer displays a warning.
With the Perform Reverse DNS Lookup setting enabled, Antigen tries to validate Domain Names or IP addresses by performing a reverse DNS lookup to compare to entries in the Antigen Allowed Mailhosts or Rejected Mailhosts lists.
This validation process can cause performance issues on the Exchange server and as a best practice, we recommend disabling the Perform Reverse DNS Lookup setting.
To address this warning, disable the Antigen Perform Reverse DNS Lookup setting.To disable the Antigen Perform Reverse DNS Lookup setting
Click Start, select All Programs, select Microsoft Antigen for Exchange, and then click Antigen Administrator.
In the Connect to Server dialog box, in the server list, select the server you want to connect to, and then click OK.
Click Settings, and then click General Options.
Under Scanning, locate the Perform Reverse DNS Lookup list, and then click Disable All.
For more information about possible Exchange Server performance issues caused by the Antigen Perform Reverse DNS Lookup setting, see Microsoft Knowledge Base article 925602, "Mail flow may stop, and many e-mail messages may remain in the mail queue when you run Antigen 8.0 for Exchange" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=925602).