Well, lets assume you ran the wizards correctly to enable Exchange, internet access, etc. If you have, you can send out e-mails all day long, but you never get any back, even by hitting "reply". Your internal e-mails through Outlook will work fine, sending and receiving, but external mail will send but not receive.
1. Ensure that all the proper ports are open on your router. You'll need 80, 443-445, 110 and 25 at a minimum open. We often also add 1723 and 3389. You want the router to redirect each of these ports to your server's internal IP address.
2. You'll need to create both a host (A) record and an MX record on the internet (through godaddy, since that's your registrar). Make mail.mortxxx.com the host address and point to the public, static IP address on your router. Make mail.mortxxx.com your MX record.
3. To reduce "certificate errors", you may need to re-run the e-mail and internet wizard to install a certificate for mail.mortxxx.com (that will be the public dns "name" of your server). This is not an essential step.
4. Once your A and MX records are set up, it will take a while to propagate through the internet (2-3 days used to be standard. Lately it's taking as little as 15 minutes). Go to DNSstuff.com or a similar site and search for the MX record on your domain. When it starts showing up, you should be good to go.
5. Test by opening a command prompt and typing "telnet mail.mortxxx.com 25". This will telnet to your server on port 25. You should get a message stating you've hit an Exchange server. That's you.
6. You do not need to create a virtual server. SBS creates a default smtp virtual server for you. You can verify this by using Exchange system manager.
Assuming you ran the wizards correctly, you've port forwarded from the router correctly and your MX record is correct, you should be up and running fine.
If not, give us a call. We do SBS installs on a daily basis.