A year from the original post, I can confirm the issue is still open (MIAB latest version, DO).
Now something different…
I have a little PHP status monitor which regularly “pings” (not really ICMP packet) SMTP port of MIAB instance.
Very hacky way to make sure the service is up. The interesting piece is that whenever I get a message from MIAB about “reverse DNS not set properly”, same moment I get the message “service down” from the monitor.
The service wakes up the next tick, so nothing dangerous here, but I am wondering what would happen if someone sends me an email right the moment this “failure” happens?