Feature Request: Block connections based on IP address or Reverse DNS

[mattschwartz03]

Hello, I think some folks might find it useful to be able to block connections based on the source IP address or Reverse DNS (or lackthereof.) I want to be able to stop some of the low effort bot activity. Some of the worst offenders don't even bother with properly configured reverse DNS so it would be nice to outrightly deny them. This is one feature that I really love about OpenSMTPD. I can use a regex statement to block certain reverse DNS hosts and a statement to block hosts that don't even have reverse DNS configured. Again, it gets rid of the low effort, low hanging bot fruit.