rayfong

At the server, are you able to connect to any other mail server using
telnet? (i.e. telnet maila.microsoft.com 25)? Verify your router has port
25 open.

Are you using DNS to delivery the email or Forward All Message to a Host?

How many network cards do you have at the SBS? Verify your settings with
306802 or 309633.
306802 How to Configure Small Business Server for Full Time Internet Access
http://support.microsoft.com/?id=306802
309633 How to Configure a SBS for Full Time Internet Access with a Single
http://support.microsoft.com/?id=309633

Check the binding order to verify internal nic is at the top.
266771 HOW TO: Change the Binding Order in Windows 2000
http://support.microsoft.com/?id=266771

You may want to check out the chapter 7.
http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechn
ol/exchange/exchange2000/proddocs/onlinebooks/confsmtp/confsmtp.asp

Ray Fong
Microsoft SBS Product Support

This posting is provided "AS IS" with no warranties, and confers no rights.