SMTP Gmail sending mail.

mail.php

<?php
// REF: https://swiftmailer.symfony.com/docs/introduction.html
// composer require "swiftmailer/swiftmailer:^6.0"

require_once './vendor/autoload.php';

$MAIL_HOST = 'smtp.gmail.com';
$MAIL_PORT = '465';
$MAIL_USERNAME = 'server@gmail.com';
$MAIL_PASSWORD = 'mypwd';
$MAIL_ENCRYPTION = 'ssl';

$RECEIVER_MAIL = 'test@yahoo.com';

// Create the Transport
$transport = (new Swift_SmtpTransport($MAIL_HOST, $MAIL_PORT, $MAIL_ENCRYPTION))
  ->setUsername($MAIL_USERNAME)
  ->setPassword($MAIL_PASSWORD);

// Create the Mailer using your created Transport
$mailer = new Swift_Mailer($transport);

// Create a message
$message = (new Swift_Message('Wonderful Subject'))
  ->setFrom(['john@doe.com' => 'John Doe'])
  ->setTo([$RECEIVER_MAIL => 'A name'])
  ->setBody('Here is the message itself');

// Send the message
$result = $mailer->send($message);

echo $result;