As an old mentor once said, solve one problem at a time 
If you’re getting that error message, you need to sort it out first. Are you running it from the correct folder? Is your virtual environment set up and activated? Start with just getting:
anvil-app-server --app MY_APP_NAME
… working correctly before you tackle the other parameters. Once that’s sorted, try passing the SMTP parameters on the command line before tackling the YAML config file.
My command line is just:
anvil-app-server --config-file anvil_app.conf
and my anvil_app.conf has:
app: MY_APP_NAME
port: 8080
manual-cert-file: MY_DIGITAL_CERT.pem
manual-cert-key-file: MY_DIGITAL_CERT_KEY.pem
smtp-host: MY.SMTP.SERVER.COM
smtp-port: 25
origin: https://MY.FQDN.COM
You’ll need to add your SMTP authentication info as well. I don’t have any additional authentication parameters for my SMTP server because of how my IT department has the VLANs setup, IP restrictions, etc.
Cheers,
Ken