I was testing the new modules v4.0.22 to see how server sets worked with the Engine module, and while trying to test it with 2 pre-existing servers I had with each pointing to different URLs (mqtt1.domain.com and mqtt2.domain.com) because they’re both behind a reverse proxy with the same public IP, it prevented me from using them because it did an IP lookup it seems and assumed they were the same MQTT server. I would think this would cause a lot of issues with a lot of cloud providers of MQTT as well as I assume they’re sharing some public IPs among multiple DNS names.
I didn’t see a way of disabling this, but I would think disabling at least the IP lookup as part of validation should be an option.