I have Windows SBS with the Exchange 2010 set up to send emails, but for some reason, none are being delivered and I am not sure how to debug this problem. I have Exchange 2010 set up with an outgoing SMTP transport that I have tried both Smart Host and DNS mechanisms. My ISP is Comcast and I have set up a Business Class account with username and password there, and this information is set up in the Smart Host, but there is no place to put it in the DNS transport. I have checked the mail queues and they are empty, and I do not get bounce back messages. The sent emails simply disappear. Before setting up the Comcast username and password, I was getting connection errors, so I believe that the emails are now at least passing on from my server. I am stuck!