I have searched through many of the postings on EE and have had no success at resolving my issue, however, they have helped to maybe fine tune the configuration. So, now it's my turn to ask the experts.
I have Exchange Server 2003 running on the same computer as SBS2003. There are no other server installations on the network. We have DSL access through a Cisco 8xx DSL router.
I want to be able to receive email directly from the internet, but before going live with our real domain emails currently hosted by our ISP through aliases, I decided to test a configuration with another domain name we have registered and are using for external access to our internal web. We have one external static IP address. We have two NIC's on our server box -- one connected to the WAN (via the Cisco router) and the other to our LAN.
I have verified the following configurations (found via various postings to EE):
1) The host and MX records appear to be appropriately setup at the external DNS. DNSreports.com correctly resolves these records. However, when checking the domain name, DNSreport.com reports there is a time out error when connecting to our mail server.
2) I have setup a reverse lookup record at our ISP for our "alternate" domain from our external IP.
3) I am forwarding traffic for port 25 on our router to the ip address of our internal exchange server.
4) In the SMTP virtual server, I have anonymous access checked under access authentication and I have "all except the list below" checked for computers allowed connection. There are no computers listed below.
5) I use GFI Essentials as a spam filter on the Exchange server. I have disabled the service, but no effect on successfully receiving emails.
6) I can telnet to our mail server on port 25 internally using both the internal ip address as well as its global name (ie, mail.externalname.com).
7) I cannot telnet to our mail server externally. I get a blank command screen.
8) I can successfully send an email internally to a user at this test email domain.