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Hi,<br />
<br />
I have a user his email gets bounds back.<br />
<br />
<i>xxx@xxx.com.au<br />
The recipient's e-mail address was not found in the recipient's e-mail system. Microsoft Exchange will not try to redeliver this message for you. Please check the e-mail address and try resending this message, or provide the following diagnostic text to your system administrator.<br />
<br />
The following organization rejected your message: mail.shareplate.biz.<br />
<br />
Diagnostic information for administrators:<br />
<br />
Generating server: polonium.mailguard.com.au<br />
<br />
xxx@xxx.com.au<br />
mail.shareplate.biz #&lt;mail.shareplate.biz #5.1.1 smtp; 550 5.1.1 User unknown&gt; #SMTP#</i><br />
<br />
Could someone please explain how to troubleshoot this issue?
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Hi,

I have a user his email gets bounds back.

xxx@xxx.com.au
The recipient's e-mail address was not found in the recipient's e-mail system. Microsoft Exchange will not try to redeliver this message for you. Please check the e-mail address and try resending this message, or provide the following diagnostic text to your system administrator.

The following organization rejected your message: mail.shareplate.biz.

Diagnostic information for administrators:

Generating server: polonium.mailguard.com.au

xxx@xxx.com.au
mail.shareplate.biz #<mail.shareplate.biz #5.1.1 smtp; 550 5.1.1 User unknown> #SMTP#

Could someone please explain how to troubleshoot this issue?

Exchange 2007 550 5.1.1 User unknown

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

Interactions between email servers and clients are governed by email protocols. The three most common email protocols are POP, IMAP and MAPI. Most email software operates under one of these (and many products support more than one).  The correct protocol must be selected, and correctly configured, if you want your email account to work.

Email Protocols

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.