Today I read Run Your Own DNS over HTTPS (DoH) Resolver on Ubuntu with DNSdist which mentioned BIND will support DoH in version 9.17, which is still in development.
I had a problem where my postfix mail system wasn’t listening on its IP address 10.1.1.123 but it was listening on 127.0.0.1. I checked my firewall settings and made sure port 25 was open, but I still couldn’t connect.
I read an article, Bind Postfix Mail Server To Localhost or Specific IP Address Only, which gave me the hint I needed.
The trick was to comment out inet_interfaces in /etc/postfix/main.cf because it was specifying loopback-only which meant postfix wasn’t listening on its other IP addresses.
I have a hosts file that defines IP addresses on the LAN for all of my virtual hosts. The good thing about using the LAN IP addresses for inter-host communication is that it’s free bandwidth. I had a problem with Postfix though, because Postfix does a reverse lookup on IP addresses to get the corresponding hostname, and the IP address Postfix has for local addresses is the LAN IP address, not the public IP address. The public IP addresses are configured with proper reverse DNS PTR records, but the local addresses weren’t. So I decided to fix that.
Basically I installed bind and configured it with PTR records for the 10.0.0.0/8 network. Now when Postfix asks for the RDNS of a LAN IP address it should get the corresponding hostname. I didn’t need to configure bind with zones for the local IP addresses, because those are all specified in my /etc/hosts file. At least I hope I don’t have to configure DNS zones for my local IP addresses in bind, because that’d just be a pain in the arse.