I cannot send/recieve email using Exchange server 2003?

Hello
I have domian controler installed on MS virtual pc 2007 and I installed exchange server 2003 on server 2003 ent SP3. I have started all necessary things in application and service but still can not send and recieve email. I am getting this error
The host ‘mail.testing.com’ could not be found. Please verify that you have entered the server name correctly. Account: ‘mail.testing.com’, Server: ‘mail.testing.com’, Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 11004, Error Number: 0x800CCC0D. Even when I change to this smtp.testing.com stillit won’t work. This is a virtual environment. I dont have any router.
Thanks in advance