Encrypt Data Between Microsoft Office Outlook And Microsoft Exchange Server. Determine whether Outlook 2007 uses encryption to secure transmission between your system and the server. Select this check box to enable encryption for greater security.

Always Prompt For Logon Credentials. Select this check box if you want Outlook 2007 to prompt you for your logon credentials each time it needs to connect to the server. This is useful if you are concerned that others who have access to your computer might be accessing your mailbox.

Logon Network Security. Specify the type of authentication to use when connecting to Exchange Server. The Password Authentication option causes Exchange Server to use Microsoft Windows NT^® LAN Manager (NTLM) challenge/response to authenticate on the server using your current logon account credentials. This is the standard authentication mechanism in Windows NT domains. Kerberos Password Authentication is the default authentication mechanism for Microsoft Windows^® 2000 Server and later domains. You can choose either of these or choose the Negotiate Authentication option to have Outlook 2007 attempt both.