Symfony 3 - Swift_Mailer - 发送电子邮件但输入失败并返回0

Question

I have a development that makes use of SwiftMailer to send Emails.

I have a Development server where it is working perfectly (with PHP 5)

And I have a production server where there is PHP 7 (and the server is very virgin, with little configuration) where it is giving these problems

The emails are sent perfectly but the mailer returns 0.

My email sending function is this:

public function sendEmail ($email) {
    $transport = \Swift_MailTransport::newInstance("localhost", 25);
    $mailer = \Swift_Mailer::newInstance($transport);

    $message = \Swift_Message::newInstance("Recuperación de Contraseña");


    if (isset($email["subject"]) && !empty($email["subject"])) {
        $message->setSubject($email["subject"]);
    }

    if (isset($email["from"]) && !empty($email["from"])) {
        $message->setFrom($email["from"]);
    }

    if (isset($email["to"]) && !empty($email["to"])) {
        $message->setTo($email["to"]);
        $message->setReadReceiptTo($email["to"]);

    }

    if (isset($email["embed_images"]) && !empty($email["embed_images"])) {
        foreach ($email["embed_images"] as $embedImage_key=>$embedImage_value) {
            if (!empty($embedImage_value)) {
                $email["embed_images"][$embedImage_key] = $message->embed(\Swift_Image::fromPath($embedImage_value));
            }
        }
    }

    $email["parameters"] = array_merge($email["parameters"], array("embed_images" => $email["embed_images"]));

    if (!isset($email["body"]) || empty($email["body"])) {
        $message->setBody(
            $this->renderView(
                $email["template"],
                $email["parameters"]
            ), 'text/html'
        );

    }

    if (isset($email["attach_images"]) && !empty($email["attach_images"])) {
        foreach ($email["attach_images"] as $attachImage_key=>$attachImage_value) {
            if (!empty($attachImage_value)) {
                $message->attach(Swift_Attachment::fromPath($attachImage_value));
            }
        }
    }

    $statusSend = true;

    $logger = new \Swift_Plugins_Loggers_ArrayLogger;
    //$logger = new \Swift_Plugins_Loggers_EchoLogger; //echo messages in real-time
    $mailer->registerPlugin(new \Swift_Plugins_LoggerPlugin($logger));



    if (!$mailer->send($message, $failures)) {
        $statusSend = false;

        echo "Failures:";
        print_r($failures);
    }

    echo $logger->dump(); //not needed if using EchoLogger plugin


    return $statusSend;
}

And passes through

if (!$mailer->send($message, $failures)) {

Is Swift_Mailer's problem? From PHP?

Thanks