Set up SMTP with Mailgun
Go to the Mailgun website and sign up first. It might require you to verify your mobile phone number and credit card. But once you verify all of these, you will get free 3 months trial, so not a bad deal.
Once you finish all verification steps, go to the 'Domains' section at the sidebar, and click 'Add New Domain' to proceed.
Now, based on what it shows, you should add those values to your domain's DNS configuration. Add all of those values step by step, and click verify button at the Mailgun console to go next.
It's mostly done now. Once your domain is verified, click the 'SMTP' menu, and you'll see the credentials for it right away. Based on that, all you need to do is set it up on your HollaEx exchange.
Your configuration should be similar to the screenshot above.