The host 'smtp.gmail.com' could not be found. Please verify that you have entered the server name correctly. Account: 'pop.gmail.com', Server: 'smtp.gmail.com', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 11001, Error Number: 0x800CCC0D

In outlook express When I click send & receive below error shows.

The host 'smtp.gmail.com' could not be found. Please verify that you have entered the server name correctly. Account: 'pop.gmail.com', Server: 'smtp.gmail.com', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 11001, Error Number: 0x800CCC0D

The host 'pop.gmail.com' could not be found. Please verify that you have entered the server name correctly. Account: 'pop.gmail.com', Server: 'pop.gmail.com', Protocol: POP3, Port: 1080, Secure(SSL): Yes, Socket Error: 11001, Error Number: 0x800CCC0D

How to solve this error

Check your mail settings as this is what's causing the error.
Gmail uses secure connection and not the normal port 25 for SMTP.
Details here: Supported POP client list - Gmail Help