How to Send Email from MongoDB Function

I want to send email to customer everytime they order something. i will be doing this using database trigger but i need function code so i can write that function.

We use an alternative workflow:

We create messages in a database with all relevant fields and status.

status: new -> picked -> sent / error

Then we have an external job (crontab, nodejs, nedemailer) checking every minute for new email docs in status new, setting them to picked, sending them via SMTP, then setting the final status to sent or error.

Be aware that sent emails can still bounce. So we have another job checking incoming emails for bounced messages and updating the database. We use a trick and write our own reference into the email header which is included in a returned message. So we know exactly which email was bounced.