When trying to use Check Out (or Check In) feature of Windows SharePoint Services (WSS) 3.0 published behind TMG in a default EBS installation, checkout fails with Error Code: 500 Internal Server Error. The request was rejected by the HTTP filter. Contact the server administrator. (12217). Resolution: You must disable normalization in order to allow URL that WSS specifies. To do this: 1. Log on to Management Server or Security Server as an administrator and launch Forefront TMG Management console 2. Select Firewall Policy in console and select Allow Authenticated Users to access Sharepoint services rule 3. Right-click on rule and choose Configure HTTP 4. Uncheck Verify normalization 5. Click OK to save changes 6. On left pane, click on Monitoring and click on Configuration tab. Refresh screen until you see that status is Synced 7. Log out of RWW and log back in to check document out.