The container will automatically look for environment variables prefixed with DOMAIN followed by a number.
DOMAIN1
DOMAIN2
DOMAIN3
...
Look for the container to perform the initial registration.
That or run the following command in the container to setup domains:
/usr/local/bin/domain-connect-dyndns setup --domain "test.com"
Use the following command to update all manually:
domain-connect-dyndns update --all