do you setup the smtp server and pop3 server account at Outlook 2007/
Go to Tools | Options | email account to confirm you have set all smtp and pop3 server information.
without these information, you are not able to send/receive email.
go to support.microsoft.com site and searching for Outlook 2007 email account setup, you will see how to set up the account but you have to check your internet service provider for pop3 and smtp information.