[otrs] Content-Transfer-Encoding and UTF-8 problem

Hello, When I set DefaultCharset to "ISO-8859-2", outgoing e-mails are sent with "Content-Transfer-Encoding: quoted-printable". When I set DefaultCharset to "UTF-8", outgoing e-mails are sent with "Content-Transfer-Encoding: 8bit". Unfortunately, several e-mail clients (Lotus, Outlook*, Mozilla) can't handle this. How can I control the "Content-Transfer-Encoding:" of the outgoing e-mail? The same problem occurs when a customer sends a unicode (utf-8) e-mail. The incoming e-mail has charset=UTF-8 and Content-Transfer-Encoding: quoted-printable, while the autoreply from OTRS is sent with charset=UTF-8 and Content-Transfer-Encoding: 8bit. Is there any solution for this? Regards, Krisztian Czako