<div>
The best thing is to asked the to whitelist your company in their spam filter. You could also make sure you don't appear on any blacklist: <a href="http://www.mxtoolbox.com/blacklists.aspx" rel="ugc">http://www.mxtoolbox.com/b<wbr />lacklists.<wbr />aspx</a><br />
&nbsp;<br />

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<div>
Since the error is coming from their server, you really need to contact their mail administrator and work with them to determine the problem. 
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<div>
Is your valid IP registered in reverse lookup zone?
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<div>
rbarnhardt, thanks for replying. &nbsp;I checked and got the results below. &nbsp;I know that my mail server is not relaying spam, since it has rely restrictions on.<br />
Is it black listed in some of them because it sees the ip address as dynamic?<br />
It's blacklisted on 10 of them, should I worry about it?<br />
<br />
Note that I omitted the whole list to save space<br />
<br />
<br />
We notice you are on a blacklist. Click here for some suggestions. <br />
&nbsp;<br />
&nbsp;Checking 209.183.16.13 against 124 known blacklists...<br />
Listed: 10 time(s)<br />
Timeouts:8<br />
&nbsp;<br />
&nbsp; <br />
&nbsp;Blacklist Name &nbsp; Status Reason TTL Response Time (ms) <br />
SORBS-BLOCK &nbsp;LISTED Dynamic IP Addresses See: Detail <br />
Return codes were: 127.0.0.10 3599 562 <br />
SORBS-DUHL &nbsp;LISTED Dynamic IP Addresses See: Detail <br />
Return codes were: 127.0.0.10 3599 547 <br />
SORBS-HTTP &nbsp;LISTED Dynamic IP Addresses See: Detail <br />
Return codes were: 127.0.0.10 3599 531 <br />
SORBS-MISC &nbsp;LISTED Return codes were: 127.0.0.10 3599 0 <br />
SORBS-SMTP &nbsp;LISTED Return codes were: 127.0.0.10 3599 0 <br />
SORBS-SOCKS &nbsp;LISTED Return codes were: 127.0.0.10 3599 0 <br />
SORBS-SPAM &nbsp;LISTED Return codes were: 127.0.0.10 3599 0 <br />
SORBS-WEB &nbsp;LISTED Return codes were: 127.0.0.10 3599 0 <br />
SORBS-ZOMBIE &nbsp;LISTED Return codes were: 127.0.0.10 3599 0 <br />
TQMCUBE &nbsp;LISTED Return codes were: 65.98.66.188 7200 0 <br />
AHBL &nbsp;OK &nbsp; 0 47 <br />
CASA-CBL &nbsp;OK &nbsp; 0 47 <br />
CASA-CBL+ &nbsp;OK &nbsp; 0 62 <br />
CASA-CDL &nbsp;OK &nbsp; 0 62 <br />
CBL &nbsp;OK &nbsp; 0 16 <br />
&nbsp;<br />

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<div>
Amirchoupani, yes. the ip is registered in reverse lookup zone
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<div>
The problem with a dynamic IP is that you could have gotten one that was previously being used for spam. A number of them mentions &quot;see details&quot;, was that a clickable link? If so, did you click it?
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<div>
rbarnhardt, I want to mention that my IP is static, it never changes; I have the same for about two years.<br />
<br />
Here are the details of the link on one of the black list database.<br />
<br />
Dynamic IP Space (LAN, Cable, DSL &amp;&nbsp;Dial Ups) &nbsp;<br />
Netblock: 209.183.16.0/27 (209.183.16.0-209.183.16.3<wbr />1) <br />
Record Created: Sun May 14 11:11:09 2006 GMT <br />
Record Updated: Sun May 14 11:11:09 2006 GMT <br />
Additional Information: [MU] Dynamic/Generic IP/rDNS address, use your ISPs mail server or get rDNS set to indicate static assignment. <br />
Currently active and flagged to be published in DNS <br />
If you wish to request a delisting please do so through the Support System. <br />
&nbsp;<br />
&nbsp;<br />

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<div class="content wysiwyg-content">
Hello, we have a customer that we are not able to send email messages to. &nbsp;No user can send messages to this specific contact, but I can send from home with no problem. &nbsp;What is the easiest way to find out if the problem is with my mail server or his. Please see message below.<br />
<br />
Mail server: Exchange 2003 SP1 on SBS 2003<br />
<br />
This message was created automatically by mail delivery software. &nbsp;Please do not reply to this message.<br />
Do not use the &quot;Resend&quot; option in your mail client, as this will not resend your original message.<br />
If you wish to resend this message, you will have to compose a new message and send it instead.<br />
<br />
A message that you sent could not be delivered to all of its recipients.<br />
<br />
The following address(es) failed:<br />
<br />
&nbsp; recipient@hiscompany.com<br />
&nbsp; &nbsp; SMTP error from remote mail server after RCPT TO:&lt;recipient@hiscompany.c<wbr />om&gt;:<br />
&nbsp; &nbsp; host hiscompany.com.s8a1.psmtp.<wbr />com [xx.xx.x.xx]:<br />
&nbsp; &nbsp; 554 No relaying allowed - psmtp
</div>
</div>


Hello, we have a customer that we are not able to send email messages to.  No user can send messages to this specific contact, but I can send from home with no problem.  What is the easiest way to find out if the problem is with my mail server or his. Please see message below.

Mail server: Exchange 2003 SP1 on SBS 2003

This message was created automatically by mail delivery software.  Please do not reply to this message.
Do not use the "Resend" option in your mail client, as this will not resend your original message.
If you wish to resend this message, you will have to compose a new message and send it instead.

A message that you sent could not be delivered to all of its recipients.

The following address(es) failed:

  recipient@hiscompany.com
    SMTP error from remote mail server after RCPT TO:<recipient@hiscompany.com>:
    host hiscompany.com.s8a1.psmtp.com [xx.xx.x.xx]:
    554 No relaying allowed - psmtp

SMTP error from remote mail server

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.