I have set up Exchange 2010. I have installed everything and am able to receive emails from external world but I cannot send to them, eg I cannot send to Yahoo. I have used the Exchange Test Connectivity here: https://testexchangeconnectivity.com and everything worked fine. I have also configured the Send Connectors and everything seems fine, yet, I cannot send emails to external addresses. Internally, everything works fine. Please help Ifeatu!