How to send mails with mime module only for specific modules? Fixed it, see answer below

On my drupal installation there are some fancy webforms which send plain text emails, turning on the mime module messes them all up. But, I need the mime module to send html mails when using simplenews newsletters.

I did the following in the settings but it has no effect (html = plain):

(http://abload.de/img/bildschirmfoto2013-11w1j7v.png)

What did I miss? How to use the mime mails only when simplenews is sending mails? I set HTML as format in newsletter settings.

Thanks!
I installed the HTML Mail module and created a new setting with Mail >> Simplenews leaving the key blank, which works fine now!