I have a problem with routing SMTP traffic to my exchange server. We are moving from a software firewall setup to a hardware firewall.
We use Symanted Hosted Mail Security to filter our mail.
We currently have 3 internet lines, 2 ADSL and 1 SDSL. All have diffferent modems, all can send SMTP traffic to the software firewall.
The software firewall routes SMTP traffic sent from Symantec to our exchange server using NAT.
I can telnet port 25 from my home PC to to the outside address of any of the modems, and I get a response from my exchange server.
We are switching to a SonicWALL NSA 2400. I have setup the device and I can VPN successfully to the device.
I do not seem to be able to get a telnet response from the exchange server when I add the mail rules to the SonicWALL.
What I've tried so far:
I have contacted the ISP i am using for testing the device and checked that no SMTP blocking is active.
I have setup a different service (Terminal Services) on the sonicwall to check that fraffic does get routed ok. Had no problems routing to the terminal server using the same setup wizard that does the mail rules. (just different service and destination in firewall/NAT)
Had an expert in sonicwall checkout the rules and setup of the sonicwall. He says it's OK.
All firmwares are latest versions on Modems, SonicWall and NIC.
Checked to make sure Perimeter IP setting are not being used in exchange (they are not, list is empty)
I can telnet from the local LAN to exhange from any server or workstation.
SMTP traffic is reaching exchange from Symantec server (Via software firewall).
If I add an external IP to the inbound rule in the Software firewall SMTP rule, that IP address can telnet exchange.
Is there something obvious I am missing here?
Can you give me any suggestions that might enable me to get mail services through my nice shiny new hardware (and not inexpensive) firewall.
Please let me know what additional information you need to help you help me.