multilingual customization of email notification templates

I have seen in WP Discuz configuration that, if I enable the WpDiscuz phrase system instead of using PO/MO files, I have access to a "Phrases" menu where I can customize email notification templates.

However, if I want to use PO/MO files, I don't have access to this menu, and I can't see, unless I'm wrong, any email notification template texts in the PO/MO file.

So, if I want to customize email notification templates in multiple languages, how do I proceed?

I would like to be able to send the email in the language associated to the user as defined in his WP user profile, personal options, language.