Image inside a mail-body

Need Help
1

Hi all,
I am developing a newsletter. There are some elements included with picture an text. It is running well except including the image. I have tried the code below. The path ist correct.
Addtional I have tried to use WWW_ROOT instead of $SERVER_NAME.
Any tipps??

    foreach ($elements as $element) {
        $message .= '<div class="body_element">';
        $message .= '<h4>';
        $message .= $element->title;
        $message .= '</h4>';
        $message .= '<div class = "element_body" > ';

        $picture = 'https://' . $_SERVER['SERVER_NAME'].'/img/' . $element->path . '/' . $element->image;
        $this->log($picture);  
        $link = '<tr><td align="left" style="background-image:url('.$picture.')"></td>';    
        $this->log($link); 
        $message .= $link; 
        $message .= '<td style="font-size:0.9em;">';
        $message .= $element->text;
        $message .= '</td></tr>';
        $message .= '</div>';
        $message .= '</div> ';
        $message .= '<hr>';
    }
2

Replace :

https://' . $_SERVER['SERVER_NAME']

to

<?php echo Router::fullBaseUrl(); ?>