chinese chars subject title are not display properly in email listing

Yesterday I just updated webmin, usermin and other related packages to the lastest.
And changed usermin and webmin language to en_UTF.

I did a test on sending a email with chinese text which is not display properly in previous version.

subject title under email listing

a email opened.

I suspected that email subject title is encoded in iso but not utf

I check the email header and got that the subject title is in iso-8559 charset

Authentication-Results:; spf=temperror (sender IP is; dkim=none; x-hmca=none
X-SID-Result: NONE
X-Message-Status: n:n
X-Message-Delivery: Vj0xLjE7dXM9MDtsPTA7YT0wO0Q9MTtHRD0yO1NDTD0w
X-Message-Info: NhFq/7gR1vQ7lXrg+qM4sebR/JGDlNgUI/tYr/fdI1ePQtD7hfQhBl3aaRw7+eNsaDM50UGCjJQ3jixDrcKFN9cHwFPy6OcSpnnY/dUuh4/GUDb89Fm6+LMrUJokjZ+I4koJtIbN6ppo0foOpeTG0ECWXsRvc3Wl
Received: from ([]) by with Microsoft SMTPSVC(6.0.3790.4900);
Thu, 10 Jan 2013 16:02:53 -0800
Received: by (Postfix, from userid 546)
id 6F49F63386E2; Fri, 11 Jan 2013 07:59:15 +0800 (HKT)
From: “Sales”
Subject: =?ISO-8859-1?Q?=E4=B8=AD=E6=96=87=E6=A8=99=E9=A1=8C?=
X-Mailer: Usermin 1.520
Date: Fri, 11 Jan 2013 07:59:15 +0800 (HKT)
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=“bound1357862355”
X-OriginalArrivalTime: 11 Jan 2013 00:02:53.0593 (UTC) FILETIME=[00C5B090:01CDEF8F]

This is a multi-part message in MIME format.

Content-Type: text/plain; charset=UTF
Content-Transfer-Encoding: quoted-printable