When you uninstall Mail Security in a clustered environment, you are prompted to unregister the Mail Security resource DLL that was configured during install. You need to unregister the Mail Security resource DLL only one time and on any of the cluster nodes.
See Removing the Mail Security resource instance from the Veritas Cluster Server
Stop Microsoft Internet Information Service (IIS) before you uninstall the product. This task ensures that all of the files that are installed with the product are removed.
To stop Microsoft IIS
On the Windows taskbar, click Start > Administrative Tools > Services.
In Services window, right-click IIS Admin Service and click Stop.
Close the Stop Other Services window.
To uninstall Mail Security
On the server on which Mail Security is installed, on the Windows taskbar, click Start > Settings > Control Panel.
In the Control Panel window, double-click Add or Remove Programs.
Click Symantec Mail Security for Microsoft Exchange, and then click Remove.
In the confirmation dialog box, click Yes.
In the Information dialog box, click OK to confirm that you have stopped IIS.
When the uninstallation is complete, click OK.
After you uninstall Mail Security, the users that you added and the groups to which you assigned them remain in the Active Directory. You can remove them manually from the Active Directory.