PHPMailer Exchange Auth - exchange-server

Question

Im trying to send an E-Mail via PHPMailer. For some Reason I dont understand the authentification fails.
I also tried different things like setting authentification to PLAIN and The Secure Method to TLS, but it doesnt seem to help.
Our Exchange has a Sending Connector, which is sending the E-Mails to our Spam Proxy, which is sending the Mails out to a Mail Server, which is encrypting the Mails with DKIM.
This is my Code:
$mail = new PHPMailer();
$mail->IsSMTP(); // set mailer to use SMTP
$mail->Host = $settings['mailserver']; // specify main and backup server
$mail->SMTPAuth = true; // turn on SMTP authentication
$mail->Port = "25";
$mail->Username = $settings['mail_domain']."\\".$settings['mail_username']; // SMTP username
echo $mail->Username;
$mail->Password = $settings['mail_password']; // SMTP password
$mail->SMTPOptions = array(
'ssl' => array(
'verify_peer' => false,
'verify_peer_name' => false,
'allow_self_signed' => true
)
);
$mail->SMTPDebug = 2;
$mail->From = $settings['mail_sender'];
$mail->AddAddress($emp_mail); // name is optional
$mail->AddReplyTo($settings['mail_sender']);
$mail->WordWrap = 50; // set word wrap to 50 characters
//$mail->AddAttachment("/var/tmp/file.tar.gz"); // add attachments
$mail->IsHTML(true); // set email format to HTML
$mail->Subject = "Neue Datei erhalten: ".$filename." - ".$_COOKIE['settings']['firmenname'];
$mail->Body = $text;
$mail->AltBody = "Bitte laden Sie diese Email in der HTML Ansicht";
if(!$mail->Send())
{
$return_code['Code'] = 500;
$return_code['Msg'] = $mail->ErrorInfo.print_r($settings);
}else{
$return_code['Code'] = "200";
}
And this is my answer:
2016-09-26 13:39:44 SERVER -> CLIENT: 220-cpanel-1.fr-hostings.at ESMTP Exim 4.87 #1 Mon, 26 Sep 2016 15:39:44 +0200
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
2016-09-26 13:39:44 CLIENT -> SERVER: EHLO transfer.feurich.com
2016-09-26 13:39:44 SERVER -> CLIENT: 250-cpanel-1.fr-hostings.at Hello cpanel-1.fr-hostings.at [92.222.157.38]
250-SIZE 52428800
250-8BITMIME
250-PIPELINING
250-AUTH PLAIN LOGIN
250-STARTTLS
250 HELP
2016-09-26 13:39:44 CLIENT -> SERVER: STARTTLS
2016-09-26 13:39:44 SERVER -> CLIENT: 220 TLS go ahead
2016-09-26 13:39:44 CLIENT -> SERVER: EHLO transfer.feurich.com
2016-09-26 13:39:44 SERVER -> CLIENT: 250-cpanel-1.fr-hostings.at Hello cpanel-1.fr-hostings.at [92.222.157.38]
250-SIZE 52428800
250-8BITMIME
250-PIPELINING
250-AUTH PLAIN LOGIN
250 HELP
2016-09-26 13:39:44 CLIENT -> SERVER: AUTH LOGIN
2016-09-26 13:39:44 SERVER -> CLIENT: 334 VXNlcm5hbWU6
2016-09-26 13:39:44 CLIENT -> SERVER: xxx=
2016-09-26 13:39:46 SERVER -> CLIENT: 535 Incorrect authentication data
2016-09-26 13:39:46 SMTP ERROR: Username command failed: 535 Incorrect authentication data
2016-09-26 13:39:46 SMTP Error: Could not authenticate.
2016-09-26 13:39:46 CLIENT -> SERVER: QUIT
2016-09-26 13:39:46 SERVER -> CLIENT: 221 cpanel-1.fr-hostings.at closing connection
2016-09-26 13:39:46 SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Any Ideas?

Answer 1

After some researches I found out, that this is actually a cPanel Problem! It seems that cPanel is redirecting Outgoing SMTP Connections to the own local Mail Server. This Option can be disabled in
Home »Server Configuration »Tweak Settings
In the cPanel Root Panel.
I just did not think of that, because I saw a Server responding. I just did not recognize, that it was the Own Webservers Mailserver, that was responding