Hmm, I was afraid of it. The forwarded email has everything in UTF-8, but I cannot see the original email header or email content encoding.
I am not sure if you would be okay with that, but could you add a test user with Author role, and subscribe it to notifications?
I am not allowed to log into your website, and I don’t know how easy it is doable to make it so that I cannot log in as Author.
Myself I have used this plugin to disable login:
If you are looking for translations, they are in /wp-content/languages/plugins/gwolle-gb*
But It is not about the translation strings, but also about the content of the entry, so I think the fault is not in the translation files.