The Examples for Developers project aims to provide high-quality, well-documented API examples for a broad range of Drupal core functionality.
The "Email Example" feature implemented by the email_example submodule can be used to send illegitimate emails to arbitrary email addresses.
Therefore, the email_example sub-module is being removed from Examples for Developers until a version demonstrating security best practices can be added back in the future. Developers who based a new module on this example should review their code.