...to answer the above question, have a look to their FAQ, which states:

How is MailNation Solutions funded?
1. Primarily, we are funded by investors, and some of our revenue is derived from donations.
2. Companies that choose to outsource to our services, of course, would have to pay. This is our primary source of financial backing. We are good at what we do, so quite naturally, companies come to us for their emailing needs.

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