Ejemplo de envío de test symfony

TestMailCommand.php

<?php
# src/AppBundle/Command/TestMailCommand.php
namespace AppBundle\Command;

use Symfony\Bundle\FrameworkBundle\Command\ContainerAwareCommand;
use Symfony\Component\Console\Input\InputArgument;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Input\InputOption;
use Symfony\Component\Console\Output\OutputInterface;


class TestMailCommand extends  ContainerAwareCommand
{
    protected function configure()  
    { 
  
        $this
            ->setName( 'app:mail:test' )
            ->setDescription( 'Envía un correo electrónico de prueba' )
            ->addArgument( 'to', InputArgument::REQUIRED, 'Destinatario del correo de prueba' )
            ->addArgument( 'from', InputArgument::REQUIRED, 'Quien envía' )
          ;
    
    }

    protected  function  execute(InputInterface $input, OutputInterface $output)
    { 
        $to = $input->getArgument( 'to' );
        $from = $input->getArgument( 'from' );
        $mailer = $this->getContainer()->get( 'mailer' );

        $message = \Swift_Message::newInstance() 
            ->setSubject( 'Mail de prueba' )
            ->setFrom( $from ) 
            ->setTo( $to )
            ->setBody( 'Este es sólo un mail de pruebas',
                'text/plain' );
        $mailer->send( $message );


        # http://symfony.com/doc/current/cookbook/console/sending_emails.html
        $spool = $mailer->getTransport()->getSpool();
        $transport = $this->getContainer()->get('swiftmailer.transport.real');
        $spool->flushQueue($transport); 

        $output->writeln( "<info>Enviado</info>" );
    }
}