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Dynamic IP Ranges and Error Codes updated

 


 

 

Understand email error messages and their codes

Introduction

When sending email, you'll occasionally receive an error message with its own code. Here's an explanation of the codes—along with a recommendation on how to fix each error. Note: In the event you need to contact your email administrator, be sure to include the error message. It contains important information.

Choose the error message you received from the menu below:


BL000000 :: Mail to Comcast is rejected and is returned with an error message containing the code BL000000. What does this mean?

Our filters have determined that email from your email server has been sent in patterns which are characteristic of spam. In an effort to protect subscribers, your email server has been blocked from sending email to the Comcast network. Mail servers are typically shared by many users so it may be the case that another party using your email server has sent spam, even if you have not.

How do I get my IP removed from the blocklist?

It is important that your email administrator is aware of their outbound spam problem to avoid being blocked by Comcast in the future. When contacting your email administrator, you should include the error message contained in the email which alerted you to this problem. This error message contains important information to help your email administrator resolve this issue. Removal requests can be sent to postmaster.comcast.net/block-removal-request.html and will require the IP address of the blocked email server. Requests submitted through this form are monitored 24 hours a day, 7 days a week to ensure a timely response.

BL000001 :: Mail to Comcast is rejected and is returned with an error message containing the code BL000001. What does this mean?

Your email could not be delivered because your sending IP address is listed on the Spamhaus Zen. This is a list of IP addresses which have been detected as sending spam and also contains dynamically assigned IP addresses which are not supposed to send email directly to email servers. Comcast uses these lists to protect its subscribers from receiving spam.

How do I remediate the block?

It is important that your email provider is aware of their outbound spam problem to avoid being blocked by Comcast in the future. When contacting your email provider, you should include the error message contained in the email that alerted you to this problem. This error message contains important information to help your email provider resolve this issue. To address this issue, either you or your email provider can visit the Spamhaus website by clicking here in order to request removal.

BL000010 :: Mail to Comcast is rejected and is returned with an error message containing the code BL000010. What does this mean?

Your email could not be delivered because your email provider is listed on the Cloudmark Sender Intelligence (CSI). CSI is a list of IP addresses which have been detected as sending spam. Comcast uses this list to protect its subscribers from receiving spam.

How do I remediate the block?

It is important that your email provider is aware of their outbound spam problem to avoid being blocked by Comcast in the future. When contacting your email provider, you should include the error message contained in the email that alerted you to this problem. This error message contains important information to help your email provider resolve this issue. To address this issue, either you or your email provider can visit the CSI website by clicking here, in order to request removal.

BL000011 :: Mail to Comcast is rejected and is returned with an error message containing the code BL000011. What does this mean?

Your email could not be delivered because your sending IP address is listed on both Cloudmark Sender Intelligence (CSI) as well as the Spamhaus Zen. Both are lists of IP addresses which have been detected as sending spam and also contain dynamically assigned IP addresses which are not supposed to send email directly to email servers. Comcast uses these lists to protect its subscribers from receiving spam.

How do I remediate the block?

It is important that your email provider is aware of their outbound spam problem to avoid being blocked by Comcast in the future. When contacting your email provider, you should include the error message contained in the email that alerted you to this problem. This error message contains important information to help your email provider resolve this issue. To address this issue, either you or your email provider can visit the CSI website by clicking here and the Spamhaus website by clicking here in order to request removal.

BL000100 :: Mail to Comcast is rejected and is returned with an error message containing the code BL000100. What does this mean?

Your email could not be delivered because your email provider is listed on the Return Path Repuation Network Blocklist. This is a list of IP addresses that have been detected as sending spam. Comcast uses this list to protect its subscribers from receiving spam.

How do I remediate the block?

It is important that your email provider is aware of their outbound spam problem to avoid being blocked by Comcast in the future. When contacting your email provider, you should include the error message contained in the email that alerted you to this problem. This error message contains important information to help your email provider resolve this issue. Either you or your email provider can visit the Return Path website by clicking here, in order to request removal.

BL000101 :: Mail to Comcast is rejected and is returned with an error message containing the code BL000101. What does this mean?

Your email could not be delivered because your email provider is listed on the Return Path Reputation Network Blacklist, as well as the Spamhaus Zen. These are lists of IP addresses which have been detected as sending spam and also contain dynamically assigned IP addresses which are not supposed to send email directly to email servers. Comcast uses these lists to protect its subscribers from receiving spam.

How do I remediate the block?

It is important that your email provider is aware of their outbound spam problem to avoid being blocked by Comcast in the future. When contacting your email provider, you should include the error message contained in the email that alerted you to this problem. This error message contains important information to help your email provider resolve this issue. To address this issue, either you or your email provider can visit the Return Path website by clicking here, and the Spamhaus website by clicking here, in order to request removal.

BL000110 :: Mail to Comcast is rejected and is returned with an error message containing the code BL000110. What does this mean?

Your email could not be delivered because your email provider is listed on both the Return Path Reputation Network Blacklist, as well as the Cloudmark Sender Intelligence (CSI). Both are lists of IP addresses which have been detected as sending spam and also contain dynamically assigned IP addresses which are not supposed to send email directly to email servers. Comcast uses these lists to protect its subscribers from receiving spam.

How do I remediate the block?

It is important that your email provider is aware of their outbound spam problem to avoid being blocked by Comcast in the future. When contacting your email provider, you should include the error message contained in the email that alerted you to this problem. This error message contains important information to help your email provider resolve the issue. To address this issue, either you or your email provider can visit the Return Path website by clicking here, and the CSI website by clicking here, in order to request removal.

BL000111 :: Mail to Comcast is rejected and is returned with an error message containing the code BL000111. What does this mean?

Your email could not be delivered because your email provider is listed on the Return Path Reputation Network Blacklist, the Cloudmark Sender Intelligence (CSI), as well as the Spamhaus Zen. These are lists of IP addresses which have been detected as sending spam and also contain dynamically assigned IP addresses which are not supposed to send email directly to email servers. Comcast uses these lists to protect its subscribers from receiving spam.

How do I remediate the block?

It is important that your email provider is aware of their outbound spam problem to avoid being blocked by Comcast in the future. When contacting your email provider, you should include the error message contained in the email that alerted you to this problem. This error message contains important information to help your email provider resolve this issue. To address this issue, either you or your email provider can visit the Return Path website by clicking here, the CSI website by clicking here, and the Spamhaus website by clicking here, in order to request removal.

DM000001 :: Mail to Comcast is rejected and is returned with an error message containing the code DM000001. What does this mean?

This message has been rejected by the Comcast mail servers due to the sending domain's published DMARC policy. The sending domain has published a DMARC reject policy and this message has not passed either DKIM or SPF authentication for the domain. For more information on DMARC, visit http://dmarc.org.

If you require additional assistance, please contact Customer Security Assurance.

ES000001 :: Mail to Comcast is rejected and is returned with an error message containing the code ES000001. What does this mean?

You have been blocked from sending to the Comcast network because we have determined that you are sending email from a dynamic/residential IP address within the Comcast domain. Comcast does not allow subscribers to send email from email servers other than smtp.comcast.net.

I don't believe my email is originating from a dynamic/residential source.

Your IP space is designated for residential Comcast service. You can send or receive email through the Comcast email servers by using our webmail application or by configuring your email client to connect properly. If you need to run your own email server, please contact our Commercial Services organization at support_biz@cable.comcast.com.

How do I get my IP removed from the blacklist?

Since you are connecting through Comcast residential IP space, this restriction cannot be lifted at this time. Please see the above instructions on "how to" options to send email without lifting this block.

ES000010 :: Mail to Comcast is rejected and is returned with an error message containing the code ES000010. What does this mean?

You have been blocked from sending to the Comcast network because we have determined that you are sending email from dynamic/residential IP space. Comcast does not allow residential / dynamic IP addresses to directly connect to our email servers. In most cases, Comcast will classify your email server's IP address as dynamic if the reverse DNS does not comply with standard static naming conventions.

How do I get my IP removed from the blocklist?

It is important that you ask your email provider to review the settings of your email server to ensure it is set up correctly so that it is not blocked by Comcast in the future. When contacting your email administrator, you should include the error message contained in the email which alerted you to this problem. This error message contains important information to help your email administrator resolve this issue.

If you require additional assistance, please contact Customer Security Assurance.

RL000001 :: Mail to Comcast is queued and I see RL000001 in my email logs. What does this mean?

Comcast has instituted rate limiting on all inbound email traffic. This step was taken to protect our customers and our email system from unwanted spam and malicious attacks. Any systems affected by this rate limit will receive a 4xx message (temp-fail) during the SMTP transaction. This message is designed to instruct the sending server to try again at a later time to deliver its email.

Our rate limiting policy is based on sender reputation, provided by SenderScore as well as authentication of the sending server, regardless of the number of domains from that server.

Recipients per HourSenderScore*
3,6000 - 15
7,200N/A & 16 - 25
14,40026 - 30
28,80031 - 50
50,40051 - 70
72,00071 - 85
86,40086 - 100
*Subject to successful authentication

If the rate-limit is impacting your ability to deliver email, shortening your server's delivery retry interval should resolve the issue.

If you require additional assistance, please contact Customer Security Assurance.

RL000002 :: Mail to Comcast is queued and I see RL000002 in my email logs. What does this mean?

Comcast has instituted rate limiting on all inbound email traffic. This step was taken to protect our customers and our email system from unwanted spam and malicious attacks. Any systems affected by this rate limit will receive a 4xx message (temp-fail) during the SMTP transaction. This message is designed to instruct the sending server to try again at a later time to deliver its email.

Our rate limiting policy is based on sender reputation and volume metrics, provided by Cloudmark, regardless of the number of domains from that server.

New IP addresses that are expected to send significant amounts of email to Comcast subscribers should start by sending low volumes of mail, increasing as time goes on. As your IP sends more email, its limit will increase daily.

If the rate-limit is impacting your ability to deliver email, shortening your server's delivery retry interval should resolve the issue.

If you require additional assistance, please contact Customer Security Assurance.

Non-Specific Error Codes

Error Code Returned For more information
421 - [Too many sessions opened] Comcast allows 25 simultaneous connections per sending IP address. This error results when that limit is exceeded.
421 - [Reverse DNS failure : Try again later] 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.

SERVFAIL response. 99.9% means that the DNS somewhere up the auth tree is misconfigured or down or very badly overloaded.
421 - [Try again later] This error results for several reasons. This error should be treated as a temp-fail and can be retried.
452 - [Too many emails sent on this session] Comcast allows 1000 emails per session. This error results when that limit is exceeded.
452 - [Too many recipients for message] Comcast allows 100 recipients per message. This error results when that limit is exceeded.
550 - [Not our customer] This error results when a message is sent to a non-existent Comcast customer. These errors should be treated as an "unsubscribe" by the sender, if a bulk mailer.
550 - [Your message could not be delivered due to too many invalid recipients] 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.
550 - [Invalid sender domain] Comcast requires that all sending domains have a valid A or MX record. This error results when neither record can be found.
550 - [Account not available] This error results when a message is sent to a Comcast account that is currently not available.
552 - [Message size exceeded] Comcast allows messages of 15MB or smaller. This error results when that limit is exceeded.
554 - [PTR lookup failure] Comcast requires all sending mail server IP addresses have a valid PTR record set up. This error results when the lookup failed.

NXDOMAIN response. One of the authoritative servers for the relevant section of the in-addr.arpa DNS tree is saying that there is no PTR record for the given IP address.

Postmaster FAQs

This page was designed to address questions on the following topics:

All policies and thresholds on this page are subject to change. This site will be updated when such changes are implemented.