SMPT mail error

I cant seem to be able to get my win 2000 machine to send emails out. I have a web server and SQL running on it. I have sharepoint server and a few other programs running which are supposed to send out emails notifying me of changes. I cannot get that to work. I have had a lot of people look at it and tell me the IP and the domain pointing to is right but its something in the server thats causing the problem and I cannot figure out what that problem is.