Outlook 2007 keeps asking for User Name and Password

SBS 2008 - Exchange 2007 - Outlook 2007

This one took me a while to figure out.  After pushing out patches to the clients and server, Outlook started asking for the User Name and Password over and over again.  Outlook would still function even if the login was canceled.  There were no errors in the event viewer on the server or the client.

Turns out one of the patches installed on the server changed some of the security settings in IIS on a few of the exchange virtual directories.

Here is what fixed it for me.

From IIS Manager check the following virtual directories (Autodiscover, EWS, Exchange, Exchweb, OAB, owa) and make sure that if the Require SSL check box is checked then make sure that Client Certificates is set to Accept or Require instead of Ignore.