Return-Path header set by qmail?

[wolfgang zeikat]

our redhat linux machine mira's sendmail is using our redhat linux qmail
server luzifer as smarthost

when users on that mira send mails, the mails contain a return-path
containing the full hostname mira.webseek.de which is not fully qualified
(just for internal LAN use) and thus causing problems.
mira's sendmail masks [EMAIL PROTECTED] as [EMAIL PROTECTED] which is
fine, but that durn return-path gets added (by qmail?)

how can i prevent/overwrite that in our qmail configuration?

wolfgang