Mail "New Message" repeatly pops up when Safari is open

When I open Safari an email message labeled "New Message" opens. As soon as I close it, it opens again making Safari unusable. I've restarted my phone, updated my phone, uninstalled and reinstalled the Mail app (it was still showing the same behavior when it was uninstalled), turned off pop-ups. None of it fixed it. What else can I do to fix this?