Hello, I who laughed more information about, Mailgun Protocol for Marketing. Transactional Emails, For example, I buying this module, installing on my site, OpenCart 18.104.22.168, would be enough to send email, in large quantity, by my site, would have no more cost, for this submission, or would have to hire some service. Thank you.
In order to use this extensión you will need to setup a "Mailgun" account. This transactional email service will let you send 10.000 emails for free by month. Over this quote you will have to pay. You can check the prices in their website.
Also, once you register in Mailgun, you will have to setup your MX domain records according with Mailgun`s instructions (is an easy process, but you will need access to administrate your DNS entries for your domain).
This extension requires that you have a Mailgun Account, and integrate the API of Mailgun with OpenCart, so you will be able to send emails using Mailgun`s API. If you exceed the quota established by mailgun you must pay to Mailgun by their service.