By default, the service postfix is not being autostarted when you run the docker container.
During the development, especially when you work with a database from production, you don't want to send emails to customers by accident.
However, if you need to send emails, you can do that by starting the postfix service:
Once the service is started, you can start sending emails.
With a high probability, the e-mails will be marked as spam and found in the spam folder.