Oh, it’s not worth to be mentioned here. Both scripts are running side by side. My client does not need merged user tables. But I provide him with a newspage, only viewable for him. On this page I use Ditto to call the latest news articles wrote by him. Then I merge the output with the "blank" template to avoid any HTML base tags. With the use of inline styles and absolute paths for the pics we have a semi automatic newsletter. I teached my client to copy the source code of that page and paste it into the poMMo news editor.
The [[Email]] snippet above is to provide the poMMo unsubscribe link:
http://mydomain/newsletter/user/update_activate.php?Email=[[Email]]
poMMo personalizes the newsletter with placeholders like that (see the poMMo tutorial).
Thats all. No big deal. poMMo is a great piece of software, like MODx is.