Voici un exemple fonctionnel avec Office365 et PHPmailer :
https://stackoverflow.com/a/41592622

<?php
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

//Load composer's autoloader
require 'vendor/autoload.php';

$mail = new PHPMailer(true);                              // Passing `true` enables exceptions
try {
    //Server settings
    $mail->SMTPDebug = 2;                                 // Enable verbose debug output
    $mail->isSMTP();                                      // Set mailer to use SMTP
    $mail->Host = 'smtp.office365.com';  // Specify main and backup SMTP servers
    $mail->SMTPAuth = true;                               // Enable SMTP authentication
    $mail->Username = 'Mon email';                 // SMTP username
    $mail->Password = '*******!';                           // SMTP password
    //$mail->SMTPSecure = 'tls';                            // Enable TLS encryption, `ssl` also accepted
    //$mail->SMTPSecure = 'ssl';
    $mail->SMTPSecure = 'starttls';
    $mail->Port = 587;                                    // TCP port to connect to
    
    //Recipients
    $mail->setFrom('[email protected]', 'Moi');
    $mail->addAddress('[email protected]', 'Lui');     // Add a recipient
    $mail->addAddress('[email protected]');               // Name is optional
    //$mail->addReplyTo('[email protected]', 'Information');
    //$mail->addCC('[email protected]');
    //$mail->addBCC('[email protected]');

    //Attachments
    //$mail->addAttachment('/var/tmp/file.tar.gz');         // Add attachments
    //$mail->addAttachment('/tmp/image.jpg', 'new.jpg');    // Optional name

    //Content
    $mail->isHTML(true);                                  // Set email format to HTML
    $mail->Subject = 'Pour tester mes messages';
    $mail->Body    = 'Mon petit sa vas?? <br> Suis à la ligne <b>Cool<b>';
    //$mail->AltBody = 'This is the body in plain text for non-HTML mail clients';

    $mail->send();
    echo 'Message has been sent';
} catch (Exception $e) {
    echo 'Erreur.';
    echo 'Mailer Error: ' . $mail->ErrorInfo;
}

2019-05-28 04:49:11 SMTP ERROR: Failed to connect to server: An attempt was made to access a socket in a way forbidden by its access permissions. (10013)
SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Erreur.Mailer Error: SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

Bonjour, j'ai un souci avec mon hebergement mutualié en fait la fonction mail() est apparement bloquée ( ne fonctionne pas) on m'a conseiller PHPMailler mais je n'y arrive pas
J'ai un email professionnel sur Office 365 et suis hebergé chez Goddady serveur windows PLESK

[PHP]<?php
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

//Load composer's autoloader
require 'vendor/autoload.php';

$mail = new PHPMailer(true); // Passing `true` enables exceptions
try {
//Server settings
$mail->SMTPDebug = 2; // Enable verbose debug output
$mail->isSMTP(); // Set mailer to use SMTP
$mail->Host = 'smtp.office365.com'; // Specify main and backup SMTP servers
$mail->SMTPAuth = true; // Enable SMTP authentication
$mail->Username = 'Mon email'; // SMTP username
$mail->Password = '*******!'; // SMTP password
//$mail->SMTPSecure = 'tls'; // Enable TLS encryption, `ssl` also accepted
//$mail->SMTPSecure = 'ssl';
$mail->SMTPSecure = 'starttls';
$mail->Port = 587; // TCP port to connect to

//Recipients
$mail->setFrom('[email protected]', 'Moi');
$mail->addAddress('[email protected]', 'Lui'); // Add a recipient
$mail->addAddress('[email protected]'); // Name is optional
//$mail->addReplyTo('[email protected]', 'Information');
//$mail->addCC('[email protected]');
//$mail->addBCC('[email protected]');

//Attachments
//$mail->addAttachment('/var/tmp/file.tar.gz'); // Add attachments
//$mail->addAttachment('/tmp/image.jpg', 'new.jpg'); // Optional name

//Content
$mail->isHTML(true); // Set email format to HTML
$mail->Subject = 'Pour tester mes messages';
$mail->Body = 'Mon petit sa vas?? <br> Suis à la ligne <b>Cool<b>';
//$mail->AltBody = 'This is the body in plain text for non-HTML mail clients';

$mail->send();
echo 'Message has been sent';
} catch (Exception $e) {
echo 'Erreur.';
echo 'Mailer Error: ' . $mail->ErrorInfo;
}[/PHP]

J'ai cette erreur :
[PHP]2019-05-28 04:49:11 SMTP ERROR: Failed to connect to server: An attempt was made to access a socket in a way forbidden by its access permissions. (10013)
SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Erreur.Mailer Error: SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting[/PHP]

Merci de m'aider