I have a Cisco 800 series router which at the moment for some reason is showing the SMTP port closed/shut and our ISP is unable to relay mail to the company network. I should be able to telnet to the router from outside to the public IP address i.e. telnet x.x.x.x 25 but I cannot now for some reason.
My question is how do I open up that port on the router to accepting incoming connections for mail, presummably I need to do that on the dialer interface. I have a NAT rule to forward to the exchange once it comes in just need to open that port up.
Thanks in advance.