I am trying to change one of my customers over to a new hosted spam filtering service, but they are unable to connect to the Exchange Server (Small Business Server 2003). Initially I thought it was the settings in the Firebox, but I have verified that the proxy rules allow traffic from any IP address on the external interface to the internal IP address of the SBS.
They are able to receive email still from their current hosted spam service.
I tested the SMTP connection using telnet on port 25 both externally and internally and get the same results. I have tested both Internet available FQDN for the server as well as IP address and localhost. From my Mac it goes about 3 seconds and then reports:
Connection closed by foreign host
From a Windows XP box in my office I get a blank command prompt Window which stays that way indefinitely until I press a key and then it immediately returns to the command prompt.
I have even tried the following on the SBS:
telnet localhost 25
without success. I looked in the Exchange System Manager under Message Delivery and don't see any restrictions there.
What else am I missing? Somewhere the servers for the old spam service are allowed and nothing else is.