TB: Problems with Charsets by Sending into NNTP

I have a Problem with my Thunderbird (V1.0.5)

TB send all Messages in UTF-8 (Windows 1225), if I used Western ISO 
8859-1 on the Send Message Font Option.

If I use 8859-15, it sends in 8859-15.

I wonder, how it goes. I don't Change this Options the last Month.

Have anyone a Solution?


Greatings
  Shanky-TMW (Germany)