No authentication methods are supported by this client in the server

When I was attempting to connect by using SMTP port 25 to Rodrunner with MS Outlook 2010 beta, an error message comes up. The settings are same in all other systems which are runs with Outlook 2003 or Outlook 2007, so it was not problem with the settings. I am getting the following error message when tried to send mail. ‘No authentication methods are supported by this client in the server’.
Please help me to solve this issue.
Thanks in advance.
