How to block software intallation via GPO ?

[mallug01]

In my environment we currently have a GPO that installs a particular program at log in (Program is an outlook spam blocker). All members of the IT OU are part of the Domain Admin Group (yes, I know let me not go there now!! ), whenever anyone in the IT OU log on to a server, the prior mentioned GPO trying to install the program on the Server. I don't want this application to be installed on the server at all for any user. (It hangs up the log in process for a long time). How do I set up a GP that denies this application install (I don't want to prevent all apps from installing) on all servers? There is an OU called Servers. How do I create a software restrict policy for a particular software, which is being pushed out by GPO. I hope this makes sense!

(The software GPO is linked to the users OU) Any help is appreciated!!

[AmaF]

You can do that with the help of proper software restriction policies. But for that you will need to read the link below. It is not worth to tell you about this in short with minimum settings. Once the settings are deployed proper, gpo will avoid any software installation on the system. There are number of things which are needed to configure to deploy software restriction policies properly.
Using Software Restriction Policies to Protect Against Unauthorized Software