How to send email from Craft 3 custom plugin?

Question

I have created custom plugin in Craft 3 and want send email to receiver or site email when user submits a form.

Answer 1

Edit: After the migration to Craft 3.1.x you should rather use this Code

/**
 * @param string                            $html
 * @param string                            $subject
 * @param array|string|\craft\elements\User $mail
 *
 * @return bool
 */
public function sendMail(string $html, string $subject, $mail): bool
{
    return Craft::$app
        ->getMailer()
        ->compose()
        ->setTo($mail)
        ->setSubject($subject)
        ->setHtmlBody($html)
        ->send();
}

Edit: this is my old answer, valid for Craft 3.0.x

This is my code to send emails in Craft 3. Let me know if you have any questions.

use craft\mail\Message;
/**

@param $html
@param $subject
@param null $mail
@param array $attachments
@return bool

*/
private function sendMail($html, $subject, $mail = null, array $attachments = array()): bool
{
    $settings = Craft::$app->systemSettings->getSettings('email');
    $message = new Message();
$message->setFrom([$settings['fromEmail'] => $settings['fromName']]);
$message->setTo($mail);
$message->setSubject($subject);
$message->setHtmlBody($html);
if (!empty($attachments) && \is_array($attachments)) {

    foreach ($attachments as $fileId) {
        if ($file = Craft::$app->assets->getAssetById((int)$fileId)) {
            $message->attach($this->getFolderPath() . '/' . $file->filename, array(
                'fileName' => $file->title . '.' . $file->getExtension()
            ));
        }
    }
}

return Craft::$app->mailer->send($message);

}