Select a mail with german umlauts or other special characters, and choose "Print Preview".
The characters are displayed correctly now in the Webbrowser.
The temporary file contains now:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta charset="UTF-8"><title></title><style>...