Adding notifiers for alerts

I am trying to add a notifier for getting alerts.
Q1) Is it possible to get alerts on Rancher dashboard even without adding a notifier?
Q2) I have installed postfix on my rancher server. It is working fine there. I have tried sending a test mail from command line. Now I am adding its details as sender in the notifier. But I am getting the following error: Failed to connect smtp server: dial tcp i/o timeout.
Can you please tell me how to set up a notifier. Please find attached the image showing the parameters I am passing.