mailcow-dockerized-docs/docs/u_e-unbound-fwd.md

If you want or have to use an external DNS service, you can either set a forwarder in Unbound or copy an override file to define external DNS servers:

!!! warning Please do not use a public resolver like we did in the example above. Many - if not all - blacklist lookups will fail with public resolvers. Important: Only DNSSEC validating DNS services will work.

Method A, Unbound

Edit data/conf/unbound/unbound.conf and append the following parameters:

forward-zone:
  name: "."
  forward-addr: 8.8.8.8 # NO NOT USE PUBLIC DNS SERVERS - JUST AN EXAMPLE
  forward-addr: 8.8.4.4 # NO NOT USE PUBLIC DNS SERVERS - JUST AN EXAMPLE

Restart Unbound:

docker-compose restart unbound-mailcow

Method B, Override file

cd /opt/mailcow-dockerized
cp helper-scripts/docker-compose.override.yml.d/EXTERNAL_DNS/docker-compose.override.yml .

Edit docker-compose.override.yml and adjust the IP.

Run docker-compose down ; docker-compose up -d.