Problem of encoding for mail sender adapter

Question

Hello, everyone.
I have faced the problem of mail sender adapter.
When someone send message with any content encoding (even UTF-8) and 8bit content type encoding the XI mail adapter corrupt special and foreign symbols. I checked the message for correct structure and encoding with tpcgw utility and it was fine. For example (this is what I can see in tcpgw)
==== Response ====
+OK
+OK Password required for user itra_xi
+OK XXXXX maildrop has 1 messages (2048 octets)
+OK 1 2048
+OK
+OK 1459 octets
Return-path:
Received: from (port=20091 helo=XXXX)
     by mx76.mail.ru with psmtp
     id 1O7UoW-0003I4-00
     for XXXXXX; Thu, 29 Apr 2010 18:34:04 +0400
Message-ID:
Subject: Message 29 4
Date: Thu, 29 Apr 2010 17:33:43 +0300
MIME-Version: 1.0
Content-Type: multipart/alternative;
     boundary="----=_NextPart_000_0018_01CAE7C2.1D0BBA60"
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 6.00.2900.5843
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579
X-Spam: Not detected
X-Mras: Ok
This is a multi-part message in MIME format.
=_NextPart_000_0018_01CAE7C2.1D0BBA60
Content-Type: text/plain;
     charset="utf-8"
Content-Transfer-Encoding: 8bit
Test
Тест
And after processing by XI mail adapter  I have this payload (XIPAYLOAD mode using mail package)
Test
Тест
The same situation with using mail package in xml document.
Any suggestions how this can be corrected?

Answer 1

I switched UTF-8 encoding during displaying of http content in tcpgw utility and all other mail clients detect it as UTF-8 and work fine. Also this problem occurs with different mail clients that are senders of the message. So it seems adapter takes each byte of cyrillic symbol (each from two) and represents it as individual symbol.
Correct me if I'm wrong. Maybe there is some configuration somewhere allowing to correct or maybe it's possible to write module to correct.. but it's quite complicated to split correct and incorrect symbols.