Postie problem

hi there. I have a wp site, and try to install and configure postie, to post from an email to the site.
I installed the plugin, i configured it… (not sure if i did it well) but, the certain is this : when i tried to test what i did, this error appeared :

Connect to Mail Host
Unable to connect. The server said: POP3 connect: Error [0] [php_network_getaddresses: getaddrinfo failed: Name or service not known]

thank you !