Connection Error in Exchange 2003

Outlook 2003 cannot connect to Exchange 2007. It is giving an error message. I have tried ‘ipconfig’ and ‘flushdns’ but it is not able to fix the problem. I have restarted the exchange server information store service, but it is also not able to fix the problem. Even the restart of exchange server is not able to solve the issue. I have changed the cache settings, but there is no change in the result. It is showing all exchange services are working properly.

I have deleted the user and created it again in the Outlook 2003 and also changed the password. I have tried with the office repair, but there is no change in the result. Outlook 2003 has been used for some months and there is no big changes made, however it is not working. Outlook 2007 is working properly. But one user doesn’t want to use Outlook 2007. If anybody knows the solution to solve this, please help me. I will be thankful for all your help.