Is there a way to suppress the Microsoft Office Customization installer warning the first time you open Outlook 2010 after the plugin has been installed? I don't want my users to get this warning and click no.

You can't pass any parameters into the MSI, but if you use active directory group policies, you can install the MSI to other users and then edit the config file to populate the host and username fields. But it should be possible if you know active directory group policy well enough.