By default, Exchange Server and Microsoft Outlook do not expose this SCL value assigned to a message - it's neither visible in any of Outlook's message views, nor inserted in message headers. It's a MAPI property of a message.
If IMF's Gateway action is set to Archive, Exchange allows you to save the SCL in message headers of archived messages. This is done using a registry hack mentioned in a previous post "IMF: Archiving spam".
You can also expose the SCL property as an additional column in Microsoft Outlook— after going through a series of steps documented in Exposing SCL (Spam Confidence Level) in Outlook on the Exchange team blog. You can then use that view in OWA as well.
Exchange Server 2007 inserts detailed anti-spam stamp in message headers. This includes both SCL and PCL values, SenderID lookup details such as the Purported Responsible Domain (PRD), SenderID status.
Here are antispam headers inserted by Exchange 2007:
Received-SPF: Pass (MyServer.MyDomain.com: domain of
=?iso-8859-1?B?QWNhaVB1cmUemail@example.com designates 18.104.22.168 as
permitted sender) receiver=MyServer.MyDomain.com; client-ip=22.214.171.124;