Email Notifications not working

New to Checkmk and running the running raw 1.6.0p21. I cannot get the notifications to work. Monitoring switch via snmp, unplug switch and see alarm within the application but not getting an email. Filled out info for email in the notification section but not getting messages.

check the association of the contact group with the host and the username.

Also is the local MTA on your monitoring server configured?

You know how to send a testmail using the console?

I am working on local MTA server configuration using postfix. I can send mail locally but cannot send mail to external email. Working on trying to get that resolved