In Hosted Messaging and Collaboration version 4.5, the minimal necessary configuration includes the following Windows SharePoint Services 3.0 servers:

• One front-end Web server.
  
• One database server on a Microsoft SQL Server 2005 cluster.
  

You must use host header mode to create Windows SharePoint Services site collections. This mode allows the creation of domain-named sites for customers using Windows SharePoint Services. Examples of domain-named sites include:

• http://mysite
  
• http://mysite.fabrikam.com