<?php

// Import PHPMailer classes into the global namespace
// These must be at the top of your script, not inside a function
use PHPMailerPHPMailerPHPMailer;
use PHPMailerPHPMailerException;

//Load composer's autoloader
require 'PHPMailer/PHPMailer.php';
require 'PHPMailer/SMTP.php';
require 'PHPMailer/Exception.php';

$mail = new PHPMailer(true);
try {
    //Server settings
    $mail->SMTPDebug = 2;
    $mail->isSMTP();
    $mail->Host = 'smtp.dominiodahostnet.com.br';
    $mail->SMTPAuth = true;
    $mail->Username = 'usuario=dominiodahostnet.com.br';
    // SMTP username
    $mail->Password = '****';
    //$mail->SMTPSecure = 'tls';
    $mail->Port = 587;

    //Recipients
    $mail->setFrom('from@dominiodahostnet.com.br', 'Mailer');
    $mail->addAddress('address@dominiodahostnet.com.br', 'Joe User');
    //$mail->addAddress('ellen@example.com');               l
    //$mail->addReplyTo('info@example.com', 'Information');
    //$mail->addCC('cc@example.com');
    //$mail->addBCC('bcc@example.com');

    //Attachments
    //$mail->addAttachment('/var/tmp/file.tar.gz');
    //$mail->addAttachment('/tmp/image.jpg', 'new.jpg');
    //Content
    $mail->isHTML(true);
    $mail->Subject = 'Here is the subject';
    $mail->Body    = 'This is the HTML message body <b>in bold!</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 'Message could not be sent.';
    echo 'Mailer Error: ' . $mail->ErrorInfo;
}

2017-09-20 17:58:23 SERVER -> CLIENT: 220 smtpq.f1.k8.com.br ESMTP Postfix
2017-09-20 17:58:23 CLIENT -> SERVER: EHLO www.dominiodahostnet.com.br
2017-09-20 17:58:23 SERVER -> CLIENT: 250-smtpq.f1.k8.com.br250-PIPELINING250-SIZE 33554432250-ETRN250-STARTTLS250-AUTH PLAIN LOGIN250-ENHANCEDSTATUSCODES250-8BITMIME250 DSN
2017-09-20 17:58:23 CLIENT -> SERVER: STARTTLS
2017-09-20 17:58:23 SERVER -> CLIENT: 220 2.0.0 Ready to start TLS
SMTP Error: Could not connect to SMTP host.
2017-09-20 17:58:23 CLIENT -> SERVER: QUIT
2017-09-20 17:58:23 SERVER -> CLIENT:
2017-09-20 17:58:23 SMTP ERROR: QUIT command failed:
SMTP Error: Could not connect to SMTP host.
Message could not be sent.Mailer Error: SMTP Error: Could not connect to SMTP host.

$mail->SMTPSecure = 'tls';

$mail->SMTPSecure = 'ssl';

;extension=php_openssl.dll

;extension=openssl.so

$mail->Username = 'usuario=dominiodahostnet.com.br';

$mail->Username = 'usuario@dominiodahostnet.com.br';

$mail->Username = 'usuario';