# Aggiunta di Gabo per permettere di inserire le immagini nel corpo del messaggio
define("EMBEDUPLOADIMAGES",1);

The problem was that it didn't work for me. No way. So I had a look into the code and I found the problem. There where no way to embed images stored in any subdirectory of what stated in:

# If you want to upload images to the FCKeditor, you need to specify the location
# of the directory where the images go. This needs to be writable by the webserver,
# and it needs to be in your public document (website) area
# the directory is relative to the root of PHPlist as set above
# This is a potential security risk, so read README.security for more information
define("FCKIMAGES_DIR","uploadimages");

Substituting filesystem_image_exists() and get_filesystem_image() functions (both in admin/class.phplistmailer.php) whith the code below worked, allowing me to embed images in mails even if them are in a directory different from uploadimages.

First of all, I added the following to the config file, just to permit embedding images when sending through cronjob and PHP-cli:

//ADDED BY GABO
$phplistRoot = '/home/mysite/public_html';
//END ADDED BY GABO
[/code]

Ecco le funzioni modificate:

[code lang="php"]
## addition for filesystem images - MODIFYED BY GABO
    function filesystem_image_exists($filename) {
      ##  find the image referenced and see if it's on the server

      $elements = parse_url($filename);
      $localfile = basename($elements['path']);

      // search for subdirectory
      $basePath = $GLOBALS['phplistRoot'].$GLOBALS['pageroot'].'/'.FCKIMAGES_DIR;
      $dir = substr($elements['path'],
                    strpos($elements['path'],FCKIMAGES_DIR)+strlen(FCKIMAGES_DIR),
                    strlen($elements['path']) -
                       strpos($elements['path'],FCKIMAGES_DIR) -
                       strlen(FCKIMAGES_DIR)-strlen($localfile));

      return is_file($basePath.$dir.$localfile);
    }

    function get_filesystem_image($filename) {
      ## get the image contents
      $elements = parse_url($filename);
      $localfile = basename($elements['path']);

      $basePath = $GLOBALS['phplistRoot'].$GLOBALS['pageroot'].'/'.FCKIMAGES_DIR;
      $dir = substr($elements['path'],
                    strpos($elements['path'],FCKIMAGES_DIR)+strlen(FCKIMAGES_DIR),
                    strlen($elements['path']) -
                       strpos($elements['path'],FCKIMAGES_DIR) -
                       strlen(FCKIMAGES_DIR)-strlen($localfile));

      if (is_file($basePath.$dir.$localfile)) {
        return base64_encode( file_get_contents($basePath.$dir.$localfile) );
      }
      return 0;
    }
    ## end addition - MODIFYED BY GABO

Hope it helps saving time to someone