Aha, tak to není omezením, ale je to bug v parseru poradny,který hlásí dlouhý text, nicméně podstatná část kódu tu je (dole je jen odeslání)

 static function mail_attachment() {
            $file = "C:\\imagesMail\\simple.jpg";
            $filename = "simple.jpg";
            $file_size = filesize($file);
            $handle = fopen($file, "r");
            $content = fread($handle, $file_size);
            fclose($handle);
            $content = base64_encode($content);

            //$content = chunk_split(base64_encode($content));
            $uid = md5(uniqid(time()));
            $name = basename($file);

// header
            $header = "From: martin <hokus@pokus.cz>\r\n";
            $header .= "Reply-To: hokus@pokus.cz\r\n";
            $header .= "MIME-Version: 1.0\r\n";
            $header .= "Content-Type: multipart/mixed; boundary=\"".$uid."\"\r\n\r\n";

// message & attachment
            $nmessage = "--".$uid."\r\n";
            $nmessage .= "Content-type:text/html; charset=iso-8859-1\r\n";
            $nmessage .= "Content-Transfer-Encoding: 7bit\r\n\r\n";
            $nmessage .= "Ahoj<img src=\"cid:image.001.src\" alt=\"IETF logo\">"."\r\n\r\n";

            $nmessage .= "--".$uid."\r\n";
            $nmessage .= "Content-Type: image/jpeg; name=\"".$filename."\"\r\n";
            $nmessage .= "Content-Transfer-Encoding: base64\r\n";
            $nmessage .= "Content-ID: <image.001.src>";
            $nmessage .= "Content-Disposition: inline; filename=\"".$filename."\"\r\n\r\n";
            $nmessage .= $content."\r\n\r\n";
            $nmessage .= "--".$uid."--";