"Password not accepted from server: 535 Incorrect authentication data" when sending with GMail and phpMailer

Question

I have the same php script running on localhost - my PC with XAMPP and on a hosted server. It works from my PC, but not from the hosted server.

When I send it from the hosted server, I get the following output:

SMTP -> ERROR: Password not accepted from server: 535 Incorrect authentication data  
SMTP -> ERROR: RCPT not accepted from server: 550-Please turn on SMTP Authentication in your mail client, or login to the 550-IMAP/POP3 server before sending your message. dev.camppage.com 550-(patchvalues.com) [205.234.141.238]:50958 is not permitted to relay through 550 this server without authentication.  
SMTP Error: The following recipients failed: [email protected] FAILED

I suspect there is a configuration setting that needs to be changed on the server, but I don't know which one. Any advice would be greatly appreciated!

Here is the code:

function send_gmail ($recipients, $subject, $message, $attachment_filenames = array()) 
{
  global $email_address, $email_password, $email_name;
  require_once ($_SERVER['DOCUMENT_ROOT']. '/php/PHPMailer/class.phpmailer.php');   

  $body  = $message;
  $body  = str_replace("\\", '', $body);
  $mail = new PHPMailer();
  $mail->CharSet = "UTF-8";
  $mail->IsSMTP();
  $mail->Host       = "smtp.gmail.com";      // sets GMAIL as the SMTP server
  $mail->SMTPDebug  = 1;                     // enables SMTP debug information (for testing) 0 - none; 1 - errors & messages; 2 - messages only
  $mail->SMTPAuth   = true;                  // enable SMTP authentication
  $mail->SMTPSecure = "ssl";                 // sets the prefix to the servier
  $mail->Port       = 465;                   // set the SMTP port
  $mail->Username   = $email_address;  // GMAIL username
  $mail->Password   = $email_password; // GMAIL password
  $mail->SetFrom($email_address);
  $mail->FromName   = $email_name;
  $mail->AddReplyTo($email_address,$email_name);
  $mail->Subject    = $subject;
  $mail->MsgHTML($body);
  $mail->IsHTML(true); // send as HTML

  if (isset ($recipients[0]))
  {
    foreach ($recipients AS $to)
    {
        $to_pieces = explode (",", $to, 2);
        $to_email = trim ($to_pieces[0]);
        if (isset ($to_pieces[1]))
            $to_name = trim ($to_pieces[1]);
        else
            $to_name = " ";
        $mail->AddAddress($to_email, $to_name);
    }
    $mail->IsHTML(true); // send as HTML

    if ($mail->Send()){
        return TRUE;
    } else {
        return FALSE;
    }
} 
else 
{
    return FALSE;
}
}

TIA

Answer 1

The solution was to enable outgoing SMTP from the server settings.

On servers running cPanel's WHM, this is located under WHM's "Tweak Settings" section.

The option is to enable/disable - choose disable.

Caveat: Making this change will redirect outgoing SMTP connections allow accounts to make direct connections which may increase your odds of getting your server blacklisted.