On the Default Received connector (found in Exchange Management Console > Server Configuration > Hub Transport > Select Server Name > A connector with name Default
) go to the properties window. On the last Permissions tab, enable "Anonymous Users" permission to be able to receive inbound mails from the Internet.
Create a Send connector for outbound mail flow with address space = *
How to Create a New Send Connector
http://technet.microsoft.com/en-us/library/aa998814.aspx
This wil fix mail flow configuration.
Outlook Web Access and Exchange 2007, Exchange 2003, and Exchange 2000 Coexistence
http://technet.microsoft.com/en-us/library/bb885041.aspx
Server Configuration > Client Access > Outlook Web Access > General Tab (RTM)
http://technet.microsoft.com/en-us/library/bb691323.aspx