[Help Exchange 2003] Đây là lỗi gì xin chỉ cách khắc phục

[dizainor]

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To: ngoc.khanh0606@gmail.com
Subject:
Sent: Mon, 23 Jul 2012 14:37:16 +0700

did not reach the following recipient(s):

ngoc.khanh0606@gmail.com on Mon, 23 Jul 2012 14:38:19 +0700
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<fpt-server.thuanphat.com #5.5.0 smtp;550-5.7.1 [210.245.80.194 1] Our system has detected an unusual rate of>

- Khi gửi mail tới gmail thì bị trả về!
Các ace nào đã từng bị xin chỉ cách khắc phục.

*** Gửi yahoo bình thường, đã check blacklist spamhaus ok,

Thanks