[sirnoggin]

Quick thought I had, you're right those services should be charging for rep management, the fact your emails aren't getting through is a sign that perhaps the IP Mailgun are using to send those mails from isn't exactly white listed. If you're sending legit traffic it's way easier and cheaper to setup a mass mailer on a server of your own with a dedicated IP and then build the reputation slowly. It doesn't take very long if your emails are legit and you have unsubscribe etc inside so people don't flag you as spammy once they get bored of you.