Disable IPv6

This is ONLY recommended if you do not have an IPv6 enabled network on your host!

If you really need to, you can disable the usage of IPv6 in the compose file. Additionally, you can also disable the startup of container "ipv6nat-mailcow", as it's not needed if you won't use IPv6.

Instead of editing docker-compose.yml directly, it is preferable to create an override file for it and implement your changes to the service there. Unfortunately, this right now only seems to work for services, not for network settings.

To disable IPv6 on the mailcow network, open docker-compose.yml with your favourite text editor and search for the network section (it's near the bottom of the file).

1. Modify docker-compose.yml

Change enable_ipv6: true to enable_ipv6: false:

networks:
  mailcow-network:
    [...]
    enable_ipv6: true # <<< set to false
    [...]

2. Disable ipv6nat-mailcow

To disable the ipv6nat-mailcow container as well, go to your mailcow directory and create a new file called "docker-compose.override.yml":

NOTE: If you already have an override file, of course don't recreate it, but merge the lines below into your existing one accordingly!

# cd /opt/mailcow-dockerized
# touch docker-compose.override.yml

Open the file in your favourite text editor and fill in the following:

version: '2.1'
services:

    ipv6nat-mailcow:
      restart: "no"
      entrypoint: ["echo", "ipv6nat disabled in compose.override.yml"]

For these changes to be effective, you need to fully stop and then restart the stack, so containers and networks are recreated:

docker-compose down
docker-compose up -d

3. Disable IPv6 in unbound-mailcow

Edit data/conf/unbound/unbound.conf and set do-ip6 to "no":

server:
  [...]
  do-ip6: no
  [...]

Restart Unbound:

docker-compose restart unbound-mailcow

4. Disable IPv6 in postfix-mailcow

Create data/conf/postfix/extra.cf and set smtp_address_preference to ipv4:

smtp_address_preference = ipv4

Restart Postfix:

docker-compose restart postfix-mailcow