We spent a month dealing with intermittent deliverables issues and had to cycle through a number of IP addresses. Deleiverbility issues due to IP reputation or receiver rate limits are fairly easy to identify and it would be great to see some more proactive assessment of problems from mailgun.

We did eventually get on a solid IP and after I spent several days calling every little local ISP that was flagging our emails based on razor2 our last deleiverbility issues went away.

One thing I'd love to see is a direct integration of mail events with Slack. Currently we pass the events through ourselves via a webhook.