ZF 1.5 - Zend_Mail and long subject lines

When sending an email via Zend_Mail with a long subject
(about 90 characters)
the whole emails gets garbled.

It seems that there is a problem with the encoding because
the email body
then contains parts of the email headers.
Is this intended behaviour, i guess not? Maybe i am doing
something wrong,
advice would be appreciated.

Thanks, ota!

Sending via Zend_Mail and stmp, utf8 encoded.

Enclosed are the first few lines without the content of the
email i will
recieve:

------------------------------------------------------------
------------

nistrator=20viazenetti?=
Date: Mon, 17 Mar 2008 18:19:00 +0100
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

... encoded email content goes here ...

------------------------------------------------------------
------------


The headers of the corresponding email, please note i
replaced some parts
because of security issues:

------------------------------------

Microsoft Mail Internet Headers Version 2.0
Received: from SERVER ([192.168.21.4]) by SERVER with
Microsoft
SMTPSVC(6.0.3790.3959);
	 Mon, 17 Mar 2008 18:04:52 +0100
Received: from localhost (localhost [127.0.0.1])
	by SERVER (Postfix) with ESMTP id E996E8992E
	for <VALIDTO.DE>; Mon, 17 Mar 2008 18:04:43 +0100
(CET)
Message-id: <3f744eee7b8bcaec47be65eef43b6507SERVER>
date: Mon, 17 Mar 2008 18:04:43 +0100
Sender: VALIDSENDER.DE
Errors-To: VALIDERRORS.DE
X-Mailer: viazenetti GmbH PHP Mailer
To: "TO NAME" <VALIDTO.DE>
From: "FROM NAME" <VALIDFROM.DE>
Subject:
=?UTF-8?Q?EXAMPLE=20WEBSITE=20WEBSITE=20-=20SUBJECT=20SUBJEC
T=20=C3=84nderung=20der=20=20-=20Administrator=
Return-Path: VALIDRETURNPATH.DE
X-OriginalArrivalTime: 17 Mar 2008 17:04:52.0437 (UTC)
FILETIME=[04350050:01C88851]
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