Topic Last Modified: 2008-01-14
The Microsoft Exchange Server Analyzer Tool reads the following registry path to determine whether the Antigen ReverseDNSLookup registry key exists and is set to a value other than 0 on Exchange 2000 Server or Exchange Server 2003 computers that have Sybari Antigen version 8.0 or Microsoft Antigen Version 9.0 installed.
HKEY_LOCAL_MACHINE \Software\Sybari Software\Antigen for Exchange\
A value other than 0 for the ReverseDNSLookup registry key, or the absence of the ReverseDNSLookup registry key, means that the Antigen Perform Reverse DNS Lookup setting is enabled.
If the Exchange Server Analyzer determines that one of the following conditions is true, the Exchange Server Analyzer displays a warning.
- The Antigen ReverseDNSLookup registry key exists on an
Exchange 2000 Server or Exchange Server 2003 that has Sybari
Antigen version 8.0 or Microsoft Antigen Version 9.0 installed and
is set to a value other than 0.
- The Antigen ReverseDNSLookup registry key does not exist
on an Exchange 2000 Server or Exchange Server 2003 that has
Sybari Antigen version 8.0 or Microsoft Antigen Version 9.0
installed. If no ReverseDNSLookup registry key exists, the
default setting of Perform Reverse DNS Lookup setting is
enabled.
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.
 Note: |
|---|
| The application to configure the Sybari Antigen products is
called Sybari Client. |
- 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).