OA is one of the greatest total security software for windows boxes. Lightest on resource, top notch secure your windows box (hopefully as to Matousec security testing assessments), not high price tags, easy uses to all users, from novice to advanced users. Of course, it still has some bugs with GUI and some minor functional be better off to be implemented (IP should be added with firewall rule instead of manual inputs by users). Since the version begins 3.x it is no more officially supporting windows server anymore although that there are not many users running server versions of windows, 2003 and 2008. I am on windows 2003 enterprise and incoming 2008ent too. Probably it is hard to support all windows OS, so OA dropped its supports on windows servers. Hope it will change soon. Outpost 2009 supports windows servers so well. I have both license of uses on OA & OP2009, in windows box, it must switch to OP2009 rather than OA. OA 3.5.x.y has issue with remembering things after system shutdown and reboot on windows server 2003 box.