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I would start with you ISP or check with the IT department from a blocked email, contact them on another account for example gmail and explain the situation. My understanding is some IT guys, meaning how they configured their servers and some ISP block dynamic ip's for spamming reasons. <br />
<br />
What does <a href="http://mxtoolbox.com" rel="ugc">http://mxtoolbox.com</a>&nbsp;tell you?
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I would start with you ISP or check with the IT department from a blocked email, contact them on another account for example gmail and explain the situation. My understanding is some IT guys, meaning how they configured their servers and some ISP block dynamic ip's for spamming reasons.

What does http://mxtoolbox.com [http://mxtoolbox.com] tell you?

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you need to send via your ISP mail server, use the 'internet email' smart host wizard in the network tab of sbs manager.
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you need to send via your ISP mail server, use the 'internet email' smart host wizard in the network tab of sbs manager.

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<div class="content wysiwyg-content">
Hi,<br />
<br />
I have a client running SBS2011 with exchange 2010. <br />
<br />
When they send to one particular email address the message stay in the queue viewer with the following error &quot;451.4.4.0 Primary Target IP Address responded with &quot;556.5.7.1 Dynamic IP Addresses are blocked. Please contact your email provider&quot;<br />
<br />
I have search the web but cannot find this exact error. Can anyone advise what this error is caused by.<br />
<br />
Thanks and kind rergards,<br />
Colin
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Hi,

I have a client running SBS2011 with exchange 2010. 

When they send to one particular email address the message stay in the queue viewer with the following error "451.4.4.0 Primary Target IP Address responded with "556.5.7.1 Dynamic IP Addresses are blocked. Please contact your email provider"

I have search the web but cannot find this exact error. Can anyone advise what this error is caused by.

Thanks and kind rergards,
Colin

Exchange 2010, Error 451.4.4.0 Primary Target IP Address responded with 556.5.7.1

An email client, email reader or more formally mail user agent (MUA) is a computer program used to access and manage a user's email. A web application that provides message management, composition, and reception functions is sometimes also considered an email client, but more commonly referred to as webmail.

Internet / Email Software

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

Small Business Server (SBS) is a line of server operating systems targeted at small businesses by bundling the operating system with a number of other Microsoft products that would normally need to be purchased or licensed separately. The most notable inclusions are Exchange, SQL Server, SharePoint and ISA/TMG (Microsoft's firewall and proxy server).