email confirmation not working

Ive tested the outgoing email from the admin panel but when i go to server error logs i find this error there : Email to Test@gmail.com from Test@gmail.com failed: Connection could not be established with host localhost :stream_socket_client(): Unable to connect to localhost:25 (No connection...

New user registration confirmation email is working fine for other email domains except gmail.. It's taking more than 5 minuets in the case of Gmail account users.. Outbound email receive at my gmail account instantly. Email transport method is set to Default but it still have the same issue...