[TYPO3-english] Language settings for Powermail and TYPO3 4.7.7

[Bert Hiddink [BENDOO e-work solutions]]

Hello,

I use Typo3 4.7.7 and Powermail 2.0.6. The plugin works like a charme, 
but the language detection fails for both the javascript and also the 
server-side validation: all messages are displayed in English while ALL 
language settings are set to Dutch "nl".

Any help/idea/hints?

Thanks in advance.

Bert