Nortel phone says Server Unreachable what can be the problem?

Make it available :). The Tftp ip that is programmed in the phone or passed out by a dhcp server is unavailable or unreachable. Tftp is typically how the phone obtains it's config. Does your phone work? You can access the phones settings by holding down the blue key and restarting the phone. There you can verify your settings or change them.

This means that the firmware is messed up and need to be reloaded using a TFTP server. I hope this helps. If you need further support you can reach me at: http://www.liveperson.com/nortel-guy

Add a computer to your network, and install Microsoft Windows Server on that computer, and enable its "DHCP-server" component. Then, this computer will supply IP-addresses for all the other computers connected to your switch.

The switch is _NOT_ a DHCP-server; therefore, you need to add a DHCP-server.

sir go to the settings >time and date >turns on the auto time zone.in this mode whether you want the clock to be automatically updated when you enter a new time zone............

Is Frontier your communications company? I suggest getting a Gmail account.

go to menu --> settings --> network configuration --> server menu and scroll down to server address and give the server ip address and save the settings and reboot

The problem is with recipient server, your server is trying to communicate with them but they are not responding right away. This maybe there server has a high security so they need to scan every emails that is trying to go through there wall.

Our company is in the business of setting up equipment and providing advice over the phone. We have hundreds of calls a day, now we use a small VOIP system. But the number of calls is already overwhelming the available pool. We need to look for an alternative.

C1B is ancient UNIStim firmware. You cannot downgrade to it. Try converting to a more recent UNIStim version. You can download firmware from www.nortel.com/support.

here you are...
This could be the problem with your signaling server , have you checked it ??
I think it is losing connectivity of T-Lan Network.