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    <title>Mail delivery error codes</title>
    <description><![CDATA[What are Comcast mail delivery error codes]]></description>
    <link>http://postmaster.comcast.net/</link>
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      <title>What are comcast mail delivery error codes</title>
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            <td><strong>Specific Error Codes</strong> </td>
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            <th width="220">Error Code Returned </th>
            <th width="280">More information </th>
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            <td>ES000001</td>
            <td align="left">This error results when mail delivery is attempted from Comcast's dynamic/residential space.  <a href="http://help.comcast.net/content/faq/ES000001"><font size="1">(Learn more)</font></a></td>
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            <td>ES000010</td>
            <td align="left">This error results when mail delivery is attempted from external dynamic/residential space. <a href="http://help.comcast.net/content/faq/ES000010"><font size="1">(Learn more)</font></a></td>
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            <td>BL000000</td>
            <td align="left">This error results when mail delivery is attempted from addresses that sent mail in patterns characteristic of spam. <a href="http://help.comcast.net/content/faq/BL000000"><font size="1">(Learn more)</font></a></td>
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            <td>BL000001</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the Spamhaus Zen Blocklist. <a href="http://help.comcast.net/content/faq/BL000001"><font size="1">(Learn more)</font></a></td>
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            <td>BL000010</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on Cloudmark CSI. <a href="http://help.comcast.net/content/faq/BL000010"><font size="1">(Learn more)</font></a></td>
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            <td>BL000011</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the Spamhaus Zen blocklist and Cloudmark CSI. <a href="http://help.comcast.net/content/faq/BL000011"><font size="1">(Learn more)</font></a></td>
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            <td>BL000100</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the SenderScore blocklist. <a href="http://help.comcast.net/content/faq/BL000100"><font size="1">(Learn more)</font></a></td>
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            <td>BL000101</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the Spamhaus Zen blocklist and the SenderScore blocklist. <a href="http://help.comcast.net/content/faq/BL000101"><font size="1">(Learn more)</font></a></td>
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            <td>BL000110</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the SenderScore blocklist and Cloudmark CSI. <a href="http://help.comcast.net/content/faq/BL000110"><font size="1">(Learn more)</font></a></td>
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            <td>BL000111</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the SenderScore blocklist, Cloudmark CSI and the Spamhaus Zen blocklist. <a href="http://help.comcast.net/content/faq/BL000111"><font size="1">(Learn more)</font></a></td>
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            <td>BL001000</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the TrendMicro MAPS RBL. <a href="http://help.comcast.net/content/faq/BL001000"><font size="1">(Learn more)</font></a></td>
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            <td>BL001001</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the TrendMicro MAPS RBL and Spamhaus Zen blocklist. <a href="http://help.comcast.net/content/faq/BL001001"><font size="1">(Learn more)</font></a></td>
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            <td>BL001010</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the TrendMicro MAPS RBL and Cloudmark CSI. <a href="http://help.comcast.net/content/faq/BL001010"><font size="1">(Learn more)</font></a></td>
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            <td>BL001011</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the TrendMicro MAPS RBL, Cloudmark CSI and Spamhaus Zen blocklist. <a href="http://help.comcast.net/content/faq/BL001011"><font size="1">(Learn more)</font></a></td>
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            <td>BL001100</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the TrendMicro MAPS RBL and SenderScore blocklist. <a href="http://help.comcast.net/content/faq/BL001100"><font size="1">(Learn more)</font></a></td>
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            <td>BL001101</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the TrendMicro MAPS RBL, SenderScore blocklist and Spamhaus Zen blocklist. <a href="http://help.comcast.net/content/faq/BL001101"><font size="1">(Learn more)</font></a></td>
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            <td>BL001110</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the TrendMicro MAPS RBL, SenderScore blocklist and Cloudmark CSI. <a href="http://help.comcast.net/content/faq/BL001110"><font size="1">(Learn more)</font></a></td>
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            <td>BL001111</td>
            <td align="left">This error results when mail delivery is attempted from addresses that are listed on the TrendMicro MAPS RBL, SenderScore blocklist, Cloudmark CSI and Spamhaus Zen. <a href="http://help.comcast.net/content/faq/BL001111"><font size="1">(Learn more)</font></a></td>
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            <td>RL000001</td>
            <td align="left">This error results when mail delivery volumes exceed the hourly limits allowed based on the sending IPs reputation. <a href="http://help.comcast.net/content/faq/RL000001"><font size="1">(Learn more)</font></a></td>
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            <td><strong>Non-Specific Error Codes</strong></td>
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            <th width="220">Error Code Returned </th>
            <th width="280">For more information </th>
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            <td align="left">421 - [Too many sessions opened]</td>
            <td align="left">Comcast allows 2 simultaneous connections per sending IP address. This error results when that limit isexceeded. </td>
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            <td align="left">421 - [Reverse DNS failure : Try again later] </td>
            <td align="left">Comcast requires all sending IP addresses have a valid rDNS. This error results when the lookup failed. This error should be treated as a temp-fail and can be retried. </td>
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            <td align="left">421 - [Try again later] </td>
            <td align="left">This error results for several reasons. This error should be treated as a temp-fail and can be retried. </td>
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            <td align="left">452 - [Too many emails sent on this session] </td>
            <td align="left">Comcast allows 1000 emails per session. This error results when that limit is exceeded. </td>
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            <td align="left">452 - [Too many recipients for message] </td>
            <td align="left">Comcast allows 1000 recipients per message. This error results when that limit is exceeded. </td>
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            <td align="left">550 - [Not our customer] </td>
            <td align="left">This error results when a message is sent to a non-existent Comcast customer. These errors should be treated as an &quot;unsubscribe&quot; by the sender, if a bulk mailer. </td>
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            <td align="left">550 - [Your message could not be delivered due to too many invalid recipients]</td>
            <td align="left">This error results when a message is sent to too many invalid recipients. As a result none of the recipients received the message. Please check your distribution list and resend. </td>
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            <td align="left">550 - [Invalid sender domain] </td>
            <td align="left">Comcast requires that all sending IPs have a valid A or MX record. This error results when neither record can be found. </td>
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            <td align="left">550 - [Account not available] </td>
            <td align="left">This error results when a message is sent to a Comcast account that is currently not available. </td>
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            <td align="left">552 - [Message size exceeded] </td>
            <td align="left">Comcast allows messages of 15MB or smaller. This error results when that limit is exceeded. </td>
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            <td align="left">554 - [PTR lookup failure] </td>
            <td align="left" valign="top">Comcast requires all sending mail server IP addresses have a valid PTR record set up. This error results when the lookup failed. </td>
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      <link>http://postmaster.comcast.net//mail-error-codes.aspx</link>
      <pubDate>Wed, 04 Mar 2009 16:06:11 GMT</pubDate>
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