We have Exchange 2003 on a SBS 2003. We have had this for many years with no problems. About 3-4 weeks ago, we stopped receiving any e-mail. At that time we were using Trend's Hosted E-mail and all of our mail was sitting there. NDRs for the mail would indicate, "timed out while sending end of data." We had an "expert" come in to look at the problem and he took Trend HES out of the picture. After that, most, but not all, of our mail started coming in. He said there was no reason he could find that our mail was not coming to us. He suggested we have our mail go to an outside server and then that server could forward it to us, that way bypassing whatever is wrong with our Exchange system. The other option was to purchase a whole new server, etc. (That is not an option.)
We have NAT enabled on our router, but no firewall. We disabled the Trend HES, but there is still an anti-spam option on Trend that runs "in-house." I can see what mail that rejects, though, so that isn't causing this. Also, I did stop that to see if it would change and it didn't. Port 25 is open.
I have researched this and possible answers. I have:
1. Run the SBS best practises tool - nothing out of the ordinary.
2. I can telnet with no problem.
3. DNS Report results don't show any problems.
4. I did netdiag with nothing out of the ordinary.
5. I tested at MX Toolbox and those tests said everything was fine.
6. I have searched Experts Exchange and tried everything I could that was suggested here.
Of note: in the smtp virtual server, current sessions, there are quite a few items that just sit there. A lot of those look like legit email that we never get. I have attached one of our email logs. It looks like a lot of those same e-mails are marked "timed out." Why would they do that and where do they go?