Mail Engine
This engine handles all outgoing emails from the Rator system. Emails are queued in the MAIL_MESSAGES + MAIL_CONTENT tables in the db. This engine connects to an SMTP server, which is specified in Parameter Setup, and sends out all waiting emails. After an email is sent, it is moved to the MAIL_MESSAGES_SENT table.
This is a standard engine and the documentation is found at Mail Engine.