The document discusses an error where Postfix is unable to connect to amavisd-new on port 10024. It occurs when Postfix tries to send emails to amavisd-new for scanning but the connection is refused. The solution is to restart both Postfix and amavisd-new services and verify using netstat that they are listening on ports 25, 10025 for Postfix and 10024 for amavisd-new.