When you install Microsoft Outlook 2010 or Office 365 on a Windows Server Operating System and configure Microsoft Outlook Trust Center under (Location: Open Outlook > click File > Options > Trust Center > Under Microsoft Outlook Trust Center click Trust Center Settings > under Trust Center select Programmatic Access > Under Programmatic Access Security) path, you will find 'Antivirus status: Invalid or Unavailable.
Windows Security Center is not supported on server operating system versions. For this reason Outlook is unable to check antivirus status when installed on a Windows Server.
Windows Server OS
SEP (Symantec Endpoint Protection) 12.x and 14.x
As per Microsoft it is not supported to install Outlook on a Server OS version hence it is unable to check the SEP antivirus status. For further queries on this request, contact Microsoft Support.