I am assuming you are installing the outlook email protection feature. My guess is that outlook can't be open when installing this feature, haven't tried it but it wouldn't pop open on an unattended install if it wasn't neccessary. So my guess is that it will also pop up on a silent install. I couldn't seem to find a definitive answer for this in our documentation, but I am sure someone here that has done it will be able to tell you for sure. On the other hand silent should mean
silient so maybe our engineers found a way around this?
Sorry I couldn't be more help,
Grant-