[imp] German Umlauts

[cyx]

Hi
I just did a new install of horde/imp from scratch. Parallel I have an older
server running an older version of horde.

Problem: Userinterface in german works fine, all the German Umlauts are
correct. But Umlauts in emails are not correct. All works fine on the old
server and I can't figure out the difference to new one. 

So anybody, any idea what to do to get the Umlauts in the mail body correct,
is it a setting in mime_drivers?

Thanks

Werner