Hi Stefan,
If the System Language on CWMS (CWMS Administration > Settings > Company Info > Language) is set to English, e-mails sent to users that don't have a user profile on CWMS will be in English.
E-mail notifications sent to users that do have CWMS profile will be in the language that is configured in their CWMS User Profile settings, that includes the host.
This is how it works when scheduling from WebEx Site.
Unfortunately, when using Productivity Tools in Outlook, the meeting notification template is populated in the language that is set in meeting's host's profile (e.g. if the host has French set in his CWMS profile as the language preference, meeting invitation in outlook will be populated using French template, and then Outlook will send that notification out containing French language).
It isn't possible to do anything in this regards on CWMS configuration side.
I hope this clarifies the expected behavior.
Kind regards,
-Dejan