I'm in the middle of setting up an Exchange 2010 Server. Currently, we use a SaaS provider for Exchange 2007 services. Some (but not all) of my users have been reporting that they are receiving Outlook/Exchange login prompts to login to the new Exchange server. This is happening without any intervention on the client's machines. The Exchange server is a member of the domain and connects to the domain site remotely through a site-to-site VPN. What can I do to prevent these login prompts from appearing? Will shutting down the new server until it is time to switch resolve these issues?

A little more info: I found that on one of the client computers, all of the settings for Outlook over HTTP had been changed (automatically) from webmail.provider.com to mail.company.com (the latter being the new server). This happened when I enabled Outlook Anywhere access on Exchange 2010. I changed the client's settings back, and everything was groovy. But, when I disabled Outlook Anywhere again, the logon prompt came back.