I was playing around with the official Docker image of RabbitMQ and I was trying to use RABBITMQ_DEFAULT_USER/RABBITMQ_DEFAULT_PASS environment variable to override the default username/password (guest/guest). I noticed that the username/password provided via the environment variables were set in the rabbitmq.conf file. Still I was neither able to access the queues using the API nor the management console. But I was able to login to the management console using the guest username.
Solution: Deleting the data directory and recreating the container solved the issue