Error: Postfix/amavisd - connect to 127.0.0.1[127.0.0.1]:10024: Connection refused

You use a Postfix setup with amavisd-new and get the following errors in your mail log:

status=deferred (connect to 127.0.0.1[127.0.0.1]:10024 Connection refused)

The solution is to restart both amavisd-new and Postfix and then check with

netstat -tap

that both are running on the ports 25 and 10025 (postfix) and 10024 (amavisd-new).