Can send but CANNOT receive

My ISP is Cox Communications. I can send messages, but cannot receive them. Been at this for two days. Keep getting protocol error in the bottom left of the screen. It says “a protocol error has occured. Is this really a POP3 server?” I have triple checked all settings. What am I doing wrong?

we would appreciate if you send us logs: go to menu Tools->Settings->Logging and check Network communication. Then restart eM Client, try to simulate the issue and send us the logs (with reference to this topic) using the same logging settings window.