Socket Error 10051 means that the destination network is unreachable.
This error means that your router has returned a 'host unreachable' ICMP packet when the connection was attempted.
Usually this means that either:
- Your Internet connection is down, so the router knows that there is no way to send data to the target computer
- The router is misconfigured, so that it doesn't believe it can communicate with the target computer
- A router or firewall is blocking the VPOP3 computer from connecting to the target computer
- Windows is misconfigured to communicate with the wrong router (only if you have two or more routers)
This error will not occur if Windows is not configured to talk to a router at all, that would give a 10065 error instead