MailerQ relies on external RabbitMQ message queues for message queueing. All incoming and outgoing emails are read from and published to RabbitMQ queues, and all results are published to such queues as well.
The messages in the queues all are JSON formatted. This means that if you develop scripts or programs that inject emails directly into a message queue, your messages must be JSON encoded as well, and must use properties that are understood by MailerQ. Scripts or programs that process results from the result queues, should be able to read in and understand the JSON formatted result objects.
If you inject mails in MIME format (for example via the SMTP interface, the spool folder or the command line interface) you can of course not make use of the JSON properties to control the delivery. The properties that you would otherwise set in the JSON can then be set using special MIME headers that can be added to the email message.