All classes that implement MailManagerInterface in Drupal 9
- class \Drupal\Core\Mail\MailManager implements MailManagerInterface uses MessengerTrait, StringTranslationTrait
- class \Drupal\Tests\Core\Mail\TestMailManager
- class \Drupal\easy_email_override\Service\MailManager implements MailManagerInterface
- class \Drupal\webprofiler\Mail\MailManagerWrapper implements MailManagerInterface uses StringTranslationTrait