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