[Dovecot] multiple Return-Path headers added using lmtp director

[Cor Bosman]

Emails arrive with 2 Return-Paths when using lmtp director. Is this something configurable in the director or is this a bug?

Return-Path: <xxxxxx at xs4all.net>
Delivered-To: <xxxxxxxx+Spam>
Received: from lmtpdirector1.xs4all.net ([194.109.26.176])
	by lmtp2.xs4all.net (Dovecot) with LMTP id gOe2E3YSkE/aEAAAYH/+MA
	for <xxxxxxxxx+Spam>; Thu, 19 Apr 2012 15:26:14 +0200
Return-Path: <xxxxxxxxx at xs4all.net>
Received: from mxdrop-builder.xs4all.nl ([194.109.23.200])
	by lmtpdirector1.xs4all.net (Dovecot) with LMTP id CnOvKTkzjU9sJQAAbddgHA
	; Thu, 19 Apr 2012 15:26:14 +0200

Regards