google應用服務mail常常收不到信？(急需幫忙3Q)

我用gmail的信箱，寄到google apps應用服務的mail，對方有時收的到，有時收不到
這個問題困擾滿久的，請幫幫忙，謝謝!

以下是信件出現內容
Delivery to the following recipient failed permanently:

xxxxxx@xxxx.org.tw

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 Requested action not taken: mailbox unavailable or not local (state 14).

----- Original message -----

MIME-Version: 1.0
Received: by 10.220.124.153 with SMTP id u25mt14103170vcr.66.1281416008949;
Mon, 09 Aug 2010 21:53:28 -0700 (PDT)
Received: by 10.220.162.65 with HTTP; Mon, 9 Aug 2010 21:53:28 -0700 (PDT)
Date: Tue, 10 Aug 2010 12:53:28 +0800
Message-ID: <AANLkTinQsxzd1RY8uS+PgWHKLWivYYa=1P8767-1mJ5F@mail.gmail.com>
Subject: 4
From: =?Big5?B?wcm0tbr0uPS5cbX4pXg=?= <xxxxxxxx@gmail.com>
Content-Type: multipart/alternative; boundary=001636b145850651a0048d70ea68