After setting up straitPortal using the straitPortal SmarTeam Suite web installation (www.straitportal.com/get), authentication of straitPortal Express is defaultly set to SmarTeam authentication.
When integrating straitPortal Express and SharePoint a common scenario is to authenticate on SmarTeam/straitPortal Express using Windows credentials (no additional logon needed).
To make this work, the following changes have to be made in the UI\web.config file (straitPortal SmarTeam Suite folder):
PersonalizationId: SharePoint
Authentication mode: Windows
Allow users: COMPUTERNAME\UserName
twitter.com/straitPortal