Php-fpm sendmail Connection refused

Issue: sendmail can’t send
OS: Debian
App/Image: richarvey/nginx-php-fpm & jwilder/nginx-proxy

Use the sendmail function, or php mail (puts it to log)
sendmail: can’t connect to remote host ( Connection refused

It seems sendmail is installed, but seems like a port mapping issue. I can run it from the console, but returns that error. Guessing it can’t network out.