使用swiftmailer发送多封电子邮件时如何绕过失败的电子邮件？

Question

I've got an email queue in a MySQL database, and via cron I process X unsent emails per minute. The problem I have is that if any specific email fails, it stops execution of the rest of the emails. In one case it was because of an SMTP authentication failure, and email processing basically came to a halt because the attempt to send the failing email kept happening. Are there other ways swiftmailer can fail that I should know about?

I'm wondering what I can do here to make this loop bulletproof? If any single email fails, I'd like to mark the record in the database with an error code (mine or swiftmailers).

Swiftmailer isn't the only way we send email, and the following method is part of a driver. What are some solutions?

public function process_queue()
{
    $result = [... a few mail queue records ...];

    foreach( $result as $params )
    {
        if( ! class_exists( 'Swift', FALSE ) )
        {
            require '/libraries/Mail/swiftmailer/lib/swift_required.php';
        }

        // Prepare transport for sending mail through SMTP
        if( $params['protocol'] == 'smtp' )
        {
            $transport = Swift_SmtpTransport::newInstance( $params['smtp_host'], $params['smtp_port'] )
                ->setUsername( $params['smtp_user'] )
                ->setPassword( $params['smtp_pass'] );
        }

        // Prepare transport for simple mail sending
        else
        {
            $transport = Swift_MailTransport::newInstance();
        }

        // Prepare swiftmailer mailer object
        $mailer = Swift_Mailer::newInstance( $transport );

        // Get a new message instance, and apply its attributes
        $message = Swift_Message::newInstance()
            ->setSubject( $params['subject'] )
            ->setFrom( [ $params['from_email'] => $params['from_name'] ] )
            ->setTo( $params['to'] )
            ->setBody( $params['body'], $params['mailtype'] );

        $mailer->send( $message );
    }
}

Answer 1

You could put the send in a try-catch block and handle any exceptions after completion of the loop.

try {
    $mailer->send($message);
} catch(Exception $exception) {
    // do something with $exception that contains the error message
}

Or you can add the second parameter to send and make use of the failures.

// Pass a variable name to the send() method
if (!$mailer->send($message, $failures))
{
  // do something with $failures that contains the error message
}

Also, Swift will return an error if setTo fails because of an invalid email address, so instead of chaining to build the message you could do each method separately and catch/handle any errors.

try {
    $message->setTo($params['to']);
} catch(Swift_RfcComplianceException $e) {
    echo "The email ".$params['to']." seems invalid";
}