当收件人未知的时候，会出现in reply to rcpt to command,下面的退信内容。经过hotmail和gmail测试都是退信。当然如出现大面积退信不排除黑名单问题或者国际带宽以及政治问题。可以使用时代电邮的海外邮件中继，拥有CDN加速发送和入站方案。

 

Undelivered Mail Returned to SenderThis is the mail system at host mail.tse-mail.com.

 

I’m sorry to have to inform you that your message could not
be delivered to one or more recipients. It’s attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The mail system

<zengp.sale@truly.com.cn>: host mail.truly.com.cn[59.37.42.20] said: 550
<zengp.sale@truly.com.cn>, Recipient unknown (in reply to RCPT TO command)

Reporting-MTA: dns; mail.tse-mail.com
X-Postfix-Queue-ID: 7CB1012E004
X-Postfix-Sender: rfc822; yao_hh@emailsos.net
Arrival-Date: Wed, 27 Aug 2014 12:20:08 +0800 (CST)

Final-Recipient: rfc822; zengp.sale@truly.com.cn
Action: failed
Status: 5.0.0
Remote-MTA: dns; mail.truly.com.cn
Diagnostic-Code: smtp; 550 <zengp.sale@truly.com.cn>, Recipient unknown

Return-Path: <yao_hh@emailsos.net >
Received: by mail.tse-mail.com (Postfix, from userid 500)
id 7CB1012E004; Wed, 27 Aug 2014 12:20:08 +0800 (CST)
Received: from mail.emailsos.net (unknown [125.88.56.132])
by mail.tse-mail.com (Postfix) with SMTP id 549BB12E001;
Wed, 27 Aug 2014 12:20:06 +0800 (CST)
Received: from YAOHUIHUI ([192.168.3.87])
(envelope-sender <yao_hh@emailsos.net>)
by 192.168.0.235 with ESMTP
for <laihb.sale@truly.com.cn>; Wed, 27 Aug 2014 12:20:03 +0800
Date: Wed, 27 Aug 2014 12:21:46 +0800
From: “yao_hh” <yao_hh@emailsos.net>
To: “=?gb2312?B?0MXA+8C1uqOx6g==?=” <laihb.sale@truly.com.cn>,
“=?gb2312?B?0MXA+8HWv6G35Q==?=” <linjunf.sale@trulypcb.cn>,
“=?gb2312?B?0MXA+87iu6rJrQ==?=” <wuhs.sale@truly.com.cn>,
“=?gb2312?B?0MXA+9T40KHF7g==?=” <zengp.sale@truly.com.cn>
References: <201408071508365155355@emailsos.net>,
<201408071510397651031@emailsos.net>,
<201408071512041254857@emailsos.net>,
<201408071532423759440@emailsos.net>,
<201408071534313124414@emailsos.net>,
<201408071536077966813@emailsos.net>,
<201408071536448288078@emailsos.net>,
<201408071537542034180@emailsos.net>,
<201408071539320464029@emailsos.net>,
<201408071540403907457@emailsos.net>,
<201408071542558758007@emailsos.net>,
<201408071547159530213@emailsos.net>,
<201408151413290936524@emailsos.net>,
<201408181715074221644@emailsos.net>
Subject: =?gb2312?B?0MXA+9DC1Pa2qbWl?=
Message-ID: <201408271221462182366@emailsos.net>
X-mailer: Foxmail 6, 15, 201, 23 [cn]
Mime-Version: 1.0
Content-Type: multipart/mixed;
boundary=”=====001_Dragon635207886436_=====”
Sender: “yao_hh” <yao_hh@emailsos.net>