framework/log/EmailTarget.php
public function init()
    {
        parent::init();
        if (empty($this->message['to'])) {
            throw new InvalidConfigException('The "to" option must be set for EmailTarget::message.');
        }
        $this->mailer = Instance::ensure($this->mailer, 'yii\mail\MailerInterface');
    }
public function init()
    {
        parent::init();
        if (empty($this->message['to'])) {
            throw new InvalidConfigException('The "to" option must be set for EmailTarget::message.');
        }
        $this->mailer = Instance::ensure($this->mailer, 'yii\mail\MailerInterface');
    }
{@inheritdoc}