<?php
       public function actionContact()
{
    $model = new ContactForm();
    if ($model->load(Yii::$app->request->post()) && $model->contact(Yii::$app->params['adminEmail'])) {
        Yii::$app->session->setFlash('contactFormSubmitted');

        return $this->refresh();
    } else {
        return $this->render('contact', [
            'model' => $model]);
    }
}
?>

<?php
 public function contact($email)
{
    $content = "<p>Email: " . $this->email . "</p>";
    $content .= "<p>Name: " . $this->name . "</p>";
    $content .= "<p>Subject: " . $this->subject . "</p>";
    $content .= "<p>Body: " . $this->body . "</p>";
    if ($this->validate()) {
        Yii::$app->mailer->compose("@app/mail/layouts/html", ["content" => $content])
            ->setTo($email)
            ->setFrom([$this->email => $this->name])
            ->setSubject($this->subject)
            ->setTextBody($this->body)
            ->send();

        return true;
    } else {
        return false;
    }
}

<?php
'mailer' => [
        'class' => 'yiiswiftmailerMailer',
        'useFileTransport' => false,
        // send all mails to a file by default. You have to set
        // 'useFileTransport' to false and configure a transport
        // for the mailer to send real emails.
     'transport' => [
        'class' => 'Swift_SmtpTransport',
        'host' => 'smtp.gmail.com',
        'username' => 'mymail@gmail.com',
        'password' => 'password',
        'port' => '587',
        'encryption' => 'tls',],
    ],
?>