Can't send emails using SwiftMailer (Symfony4): wrong SMTP parameters? - symfony

Question

I'm coding a small website using Symfony 4.
There's a simple contact form that is supposed to send emails, seemed easy until I realize I can't configure it ^^
I've followed Symfony doc instructions from here:
[https://symfony.com/doc/current/email.html][1]
Meaning mainly having the Swift mailer dependy:
composer require mailer
And my Controller looks like this:
/**
* #Route("/contact", name="contact_handling")
*/
public function contactHandler(Request $request, \Swift_Mailer $mailer)
{
$contact = new Contact();
$form = $this->createForm(ContactType::class, $contact);
$form->handleRequest($request);
if ($form->isSubmitted() && $form->isValid()) {
$message = (new \Swift_Message('Hello Email'))
->setFrom('send#example.com')
->setTo('myownemail#hotmail.fr')
->setBody("plopppp mail")
;
$mailer->send($message);
$contact = $form->getData();
return $this->render('home.html.twig', array(
'form' => $form->createView(),
));
}
return $this->render('home.html.twig', array(
'form' => $form->createView(),
));
No matter what it does next in the return (I'm also trying to figure out how to avoid the page reload and just return an answer like "OK" or "not OK" then my Javascript pops up a message)
For dev environment (I'll have the same problem when moving to prod by the way),
my .env conf file has this parameter:
MAILER_URL=smtp://smtp-mail.outlook.com:587?encryption=tls&username=myownemail#hotmail.fr&password=mypwd
while trying to use my own email account, which could be my problem
Smtp address, port and encryption are some parameters found on website like this one:
[https://www.lifewire.com/what-are-the-outlook-com-smtp-server-settings-1170671][1]
Of course, I've never received anything.
If someone familiar whith this could help me it would be very nice :)
I'm using Windows10 + PhpStorm + php7 + built-in symfony server
Thanks!
Edit:
Output from: php bin/console debug:config SwiftmailerBundle
swiftmailer:
default_mailer: default
mailers:
default:
url: '%env(MAILER_URL)%'
spool:
type: memory
path: 'C:\www\h4h\var\cache\dev/swiftmailer/spool'
id: null
transport: smtp
command: '/usr/sbin/sendmail -bs'
username: null
password: null
host: localhost
port: null
timeout: 30
source_ip: null
local_domain: null
encryption: null
auth_mode: null
delivery_addresses: { }
logging: true
delivery_whitelist: { }
Edit 2:
I've just tried putting the conf in the config/packages/swiftmailer.yaml without more success, but at least, php bin/console debug:config SwiftmailerBundle outputs the correct info:
swiftmailer:
transport: gmail
username: mylogin
password: mypwd
host: smtp.gmail.com
port: 587
encryption: ssl
auth_mode: login
spool:
type: file
path: '%kernel.cache_dir%/swiftmailer/spool'
sender_address: ~
antiflood:
threshold: 99
sleep: 0
delivery_addresses: []
disable_delivery: ~
logging: '%kernel.debug%'