Ok, I have no knowlege of MS Exchange until a few weeks ago when i was put in charge of the Exchange server. I'm an intern at a company that only really has 2 tech guys. So the Exchange server stopped recieving emails yesterday. We are running exchange 2003 sp2 on Server 2003 on our IBM x235. When i send an email out (within the company) and then reply to that email (with my gmail account)I can recieve an email back. Now I am more than sure everything is set correctly. I have had a friend of mine help me out through the day and were at a loss. Emails are now going out after not all day long so part of the problem is gone. We are at a loss. I took the firewall out of the picture for the time being so that isnt an issue.

Check your MX records and you ISP to start with. And, if it is urgent, get someone in instead of messing with something you have no experience with, you could do much more damage than you would like.

I have confirmed the MX records are correct. All the NAT settings in the router are correct. There is no firewall. Running a dns report on our domain came up with everything correct. I uninstalled GFI Mail Essentials as well. That didn't seem to do the trick either.

Do some other tests then, from a remote location: http://support.microsoft.com/default.aspx?scid=kb;en-us;Q153119