Call to undefined function Zend\Mail\Header\iconv_mime_decode()

[Unreality1987]

I use zend-mail to send an register mail through SMTP with TLS and plain auth.

Here is the used code:

<?php

namespace App\Mail\Service;

use Zend\Mail\Transport\Smtp;
use Zend\Mail\Transport\SmtpOptions;
use Zend\Mail\Message;

class MailService
{
    private $transport;
    private $options;
    
    public function __construct() {
        $this->transport = new Smtp();
        $this->options =  new SmtpOptions([
            'name' => 'XXXXXX',
            'host' => 'XXXXXX',
            'port' => 587,
            'connection_class'  => 'plain',
            'connection_config' => [
                'username'  => 'XXXXXX',
                'password'  => 'XXXXXX',
                'ssl'       => 'tls'
            ],
        ]);
        $this->transport->setOptions($this->options);
    }
    
    public function sendRegisterMail($email)
    {
        $message = new Message();
        $message->addFrom('XXXXXX', 'XXXXXX');
        $message->addTo($email);
        $message->setEncoding("UTF-8");
        $message->getHeaders()->addHeaderLine('Content-Type', 'text/plain; charset=UTF-8');
        $message->setSubject('Subject');
        $message->setBody('This is the Message Body');
        
        $this->transport->send($message);
        
    }
}

?>

When I'm calling this function the above error message appears. ICONV is installed and working, even NetBeans 8.2 recognizes the function in autocomplete. So I have no idea why this error occurs.

Regards,
Unreality

[Unreality1987]

Although iconv seemed to be enabled, it wasn't in php.ini