Dispatch an Event when the a user logs
Once you get the event working, all you have to do is create an instance of the Logger Class in the Logger folder inside your module.

In here:
 /drupal_root/web/module/custom/my_module/src/Logger

And the class will be something like:

namespace Drupal\my_module\Logger;


use Drupal\Core\Logger\RfcLoggerTrait;
use Psr\Log\LoggerInterface;

class SendToEmail implements LoggerInterface {

  use RfcLoggerTrait;

  /**
   * Logs with an arbitrary level.
   *
   * @param mixed $level
   * @param string $message
   * @param array $context
   *
   * @return void
   */
  public function log($level, $message, array $context = []) {
    //Building the parameters for the email
    $params['level'] = $level;
    $params['message'] = $message;
    $params['context'] = $context;
    $this-&gt;sendEmail($params);
  }

  /**
   * @param array $params
   *
   * @return null
   */
  public function sendEmail($params = array()){
    //Variable declaration
    $module = 'my_module';
    $key = 'my_module_message';
    $to = "email@email.com";
    $from = "email@email.com";
    $language_code = \Drupal::service('language_manager')-&gt;getDefaultLanguage()-&gt;getId();
    $send_now = TRUE;

   $mail = \Drupal::service('plugin.manager.mail')-&gt;mail($module, $key, $to, $language_code, $params, $from, $send_now);
    return $mail;
  }
}