Vigor 2950 Firmware v3.2.1
Only WAN1 is active (connected to Zen Internet via a router in bridging mode). One fixed public IP address. All working well apart from port 25 forwarding to exchange server. Other port forwarding (3389 for example) works perfectly well. Have tried port forwarding and open ports both with the same result. Exchange server is definitely working. Zen do not block port 25.
Mapping external port 25 to internal port 25 does not work. When telnetting on port 25 to public IP it seems to connect but there is no SMTP banner.
This is the strange bit.....if I map other external ports to internal port 25 then it works! So for example, map external port 26 to internal port 25 and then telnet to port 26 on the public IP and it works perfectly. Have tried 10 different external ports and they all work.
It seems that the 2950 is partially blocking port 25 but I cannot see any parameters for this. There are no firewall rules in place other than the defaults.
Any help would be appreciated as I have spent days on this.
