Former mailgun customer. Asked them to delete my personal data a couple of weeks ago (I was not able to do it myself... ) because I would rather they don't leak it in a security hiccup. They kindly refused to do so (as I don't believe any tech support can be that incompetent) and kept spamming my inbox instead. While the severity of this incident is not clear, never imagined curses can act on such a short notice.
This is because Mailgun is in the practice of spam. The number of spam campaigns I've seen with Mailgun as the conduit is high, second only to Mailchimp.
This is Chris from the Mailgun team. I'm sorry that this happened, this shouldn't have been the case. I'd be happy to help rectify this issue, would you be able to send an email to help@mailgun.com with details so I can review?