Microsoft has a freely available tool for download called the External Collaboration Toolkit for Sharepoint which is intended to help with extranet access scenarios. It consists of software and guidance that will help you to deploy a customizable solution built on Microsoft Windows SharePoint Services 3.0 or Microsoft Office SharePoint Server 2007 that teams can use to collaborate securely with partners outside the firewall. For more info: http://technet.microsoft.com/en-us/library/cc268155.aspx

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