How to use Outlook policy to control credential prompts when connecting to an Exchange Server mailbox

1. Click Start, click Run, type regedit, and then click OK.
2. In the Registry Editor, locate the following key for Outlook 2013:
   
   HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\xx.0\Outlook\Security
   
   Where xx.0 is 15.0 for Outlook 2013, 14.0 for Outlook 2010, 12.0 for Outlook 2007, and 11.0 for Outlook 2003
3. Point to New, and then click DWORD Value.
4. Type PromptForCredentials as the name of the new registry entry, and then press ENTER.
5. In the right pane, right-click PromptForCredentials, and then click Modify.
6. In the Edit DWORD Value dialog box, and then type one of the following values in the Value data dialog box:
   
   

   Value	Description
   0	Cached credentials are used.
   1	Cached credentials cannot be used. You are always prompted for logon credentials.

7. Click OK.