I've created a docker container that runs postfix in the foreground using postfix start-fg. It starts fine but is having trouble resolving hostnames, which I think is due to that /var/spool/postfix/etc is missing. This is mentioned in a comment here but without any explanation or reference.
There is a workaround described here, with a vague explanation and no sources.
Is this described in the official documentation or is it just something that people discover after hours of debugging?