When you send an email to a Comcast.net email address, you may get an error message with its own code. Learn about the codes with tips on how to fix them here.
If you need to contact an email administrator, be sure to include the error message. It includes important information.
Error codes and messages
BL000000
Meaning: Filters found that email from your server was sent in patterns that seem like spam. To protect customers, your email server was blocked from sending email to the Xfinity network. Mail servers are often shared by many users, so it is possible someone else using your server sent spam.
Fix: Tell your email provider about the problem to avoid blocks in the future. When you contact your email administrator, include all error details in the email. This is needed to help fix the issue. Removal requests can be submitted at Customer Security Assurance Postmaster site. The request needs the IP address of the blocked email server. Requests submitted through this form are monitored 24 hours a day, seven days a week.
BL00001 through BL001111
If you got an error BL00001 through BL001111, your email could not be delivered because it was detected as being spam and was on one or more spam lists.
To fix this issue, tell your email provider about the problem to avoid blocks in the future. When you contact your email administrator, include all error details in the email. This is needed to help fix the issue. You can then go to the websites below to request removal.
- BL000001: Listed on the Spamhaus Zen. Go to the Spamhaus website to request removal.
- BL000010: Listed on Cloudmark Sender Intelligence (CSI). Go to the CSI website to request removal.
- BL000011: Listed on both the CSI and Spamhaus Zen lists. Go to the CSI website and Spamhaus website to request removal.
- BL000100: Listed on the Return Path Reputation Network Blocklist. Go to the Return Path website to request removal.
- BL000101: Listed on the Return Path Reputation Network Blocklist and the Spamhaus Zen. Go to the Return Path website and Spamhaus website to request removal.
- BL000110: Listed on both the Return Path Reputation Network Blocklist and CSI list. Go to the Return Path website and the CSI website to request removal.
- BL000111: Listed on the Return Path Reputation Network Blocklist, CSI, and Spamhaus Zen. Go to the Return Path website, CSI website, and Spamhaus website to request removal.
- BL001000: Listed on the Vade Threat List (VTL). Go to the Vade website to request removal.
- BL001001: Listed on VTL and Spamhaus Zen. Go to the Vade website and Spamhaus website to request removal.
- BL001010: Listed on the VTL and CSI. Go to the Vade website and the CSI website to request removal.
- BL001011: Listed on the VTL, CSI, and Spamhaus Zen. Go to the Vade website, the CSI website, and the Spamhaus website to request removal.
- BL001100: Listed on the VTL and the Return Path Reputation Network Blacklist. Go to the Vade website and Return Path website to request removal.
- BL001101: Listed on the VTL, the Return Path Reputation Network Blacklist, and Spamhaus Zen. Go to the Vade website, the Return Path website, and the Spamhaus website to request removal.
- BL001110: Listed on the VTL, the Return Path Reputation Network Blacklist, and CSI. Go to the Vade website, the Return Path website, and the CSI website to request removal.
- BL001111: Listed on the VTL, the Return Path Reputation Network Blacklist, CSI, and Spamhaus Zen. Go to the Vade website, the Return Path website, the CSI website, and the Spamhaus website to request removal.
DM000001
Meaning: This message was rejected by the Xfinity mail servers due to the sending domain's published DMARC policy. The message has not passed either DKIM or SPF authentication for the domain. For more on DMARC, go to dmarc.org.
Fix: If you need more help:
- Go to the Customer Security Assurance website.
- Click the Postmaster square.
- Scan the FAQs for your issue.
- If your issue is not fixed, scroll down to click Report an issue.
ES000001
Meaning: You have been blocked from sending to the Xfinity network. We found you are sending email from a dynamic/residential IP address within the Xfinity domain. Xfinity does not let customers send email from email servers other than smtp.comcast.net.
Fix: You can send or receive email through Xfinity email servers with the webmail app. You can also configure your email client to connect properly. If you need to run your own email server, consider a Comcast Business account.
ES000010
Meaning: You have been blocked from sending to the Xfinity network. We found you are sending email from dynamic/residential IP space. Xfinity does not allow these IP addresses to connect to our email servers. In most cases, Xfinity classifies your email server's IP address as dynamic if the reverse DNS does not comply with standard static naming conventions.
Fix: Ask your email provider to review your email server’s settings. They can help make sure it’s set up correctly so it’s not blocked. When you contact your email administrator, include all error details in the email. This is vital information to help fix the issue. If you need more help:
- Go to the Customer Security Assurance website.
- Click the Postmaster square.
- Scan the FAQs for your issue.
- If your issue is not fixed, scroll down to click Report an issue.
ODM00001
Meaning: This message was rejected by the Xfinity outbound mail servers due to Xfinity’s published DMARC policy. The message has not passed either DKIM or SPF authentication for the domain. For more on DMARC, go to dmarc.org.
Fix: If you need more help:
- Go to the Customer Security Assurance website.
- Click the Postmaster square.
- Scan the FAQs for your issue.
- If your issue is not fixed, scroll down to click Report an issue.
RL000001
Meaning: Xfinity has rate limits on all inbound email traffic. This protects customers and the email system from unwanted spam and malicious attacks. Systems affected by this rate limit get a 4xx message (temp-fail) during the SMTP transaction. This message tells the sending server to try to deliver the email again later.
The rate limit policy is based on:
- Sender reputation provided by SenderScore.
- Authentication of the sending server, no matter the number of domains from that server.
| Recipients per hour | SenderScore* |
| 120 | Not applicable |
| 1,200 | 0–15 |
| 3,600 | 16–25 |
| 6,000 | 26–30 |
| 12,000 | 31–50 |
| 24,000 | 51–70 |
| 42,000 | 71–85 |
| 60,000 | 86–100 |
| *Subject to successful authentication | |
Fix: If the rate limit impacts your ability to deliver email, shorten your server's delivery retry interval. If you need more help:
- Go to the Customer Security Assurance website.
- Click the Postmaster square.
- Scan the FAQs for your issue.
- If your issue is not fixed, scroll down to click Report an issue.
RL000002
Meaning: Xfinity has rate limits on all inbound email traffic. This protects customers and the email system from unwanted spam and malicious attacks. Systems affected by this rate limit get a 4xx message (temp-fail) during the SMTP transaction. This message tells the sending server to try to deliver the email again later.
The rate limit policy is based on sender reputation and volume metrics, provided by Cloudmark, no matter the number of domains from that server.
New IP addresses expected to send large amounts of email to Xfinity customers should start by sending low volumes of mail. Then, increase as time goes on. As your IP sends more email, its limit will increase daily.
Fix: If the rate limit impacts your ability to deliver email, shorten your server's delivery retry interval. If you need more help:
- Go to the Customer Security Assurance website.
- Click the Postmaster square.
- Scan the FAQs for your issue.
- If your issue is not fixed, scroll down to click Report an issue.
RL000003
Meaning: Xfinity has rate limits on all inbound email traffic. This protects customers and the email system from unwanted spam and malicious attacks. Systems affected by this rate limit get a 4xx message (temp-fail) during the SMTP transaction. This message tells the sending server to try to deliver the email again later.
This rate limit policy is based on historical volumes and quality of that volume. The limits applied are independent of the number of domains coming from a given IP. This policy should apply to both IPv4 and IPv6.
New IP addresses expected to send large amounts of email to Xfinity customer should start by sending low volumes of mail. Then, increase as time goes on. As your IP sends more email, its limit will increase daily.
Fix: If the rate limit impacts your ability to deliver email, shorten your server's delivery retry interval. If you need more help:
- Go to the Customer Security Assurance website.
- Click the Postmaster square.
- Scan the FAQs for your issue.
- If your issue is not fixed, scroll down to click Report an issue.
Other error codes
| Error code returned | For more information |
| Xfinity | Xfinity allows 25 simultaneous connections per sending IP address. This error shows when that limit is exceeded. |
| 421 — [Reverse DNS failure : Try again later] | Xfinity requires all sending IP addresses have a valid rDNS. This error shows when the lookup failed. It should be treated as a temporary fail. It should be tried again later. SERVFAIL response. 99.9% means that the DNS somewhere up the auth tree is misconfigured, down, or very badly overloaded. |
| 421 — [Try again later] | This error happens for several reasons. It should be treated as a temporary fail. It should be tried again later. |
| 452 — [Too many emails sent on this session] | Xfinity allows 1,000 emails per session. This error shows when that limit is exceeded. |
| 452 — [Too many recipients for message] | Xfinity allows 100 recipients per message. This error shows when that limit is exceeded. |
| 550 — [Not our customer] | This error shows when a message is sent to an Xfinity customer that doesn’t exist. It 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] | Xfinity requires that all sending domains have a valid A or MX record. This error shows when neither record can be found. |
| 550 — [Account not available] | This error shows when a message is sent to a Xfinity account that is currently not available. |
| 552 — [Message size exceeded] | Xfinity allows messages of 15 MB or smaller. This error shows when that limit is exceeded. |
| 554 — [PTR lookup failure] | Xfinity requires all sending mail server IP addresses have a valid PTR record set up. This error shows 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. |
Mail servers are often shared by many users. It is possible someone else using your server sent spam, even if you did not.
Make your email administrator aware of the spam problem to avoid being blocked in the future. Removal requests can be sent to the Customer Security Assurance Postmaster website. Be sure to include the IP address of the blocked mail server. Below is an example of an error message and where you can find the IP address needed for your removal request. You can also get this from your email administrator.
Below is an example of an error message and where you can find the IP address needed for your removal request. You can also get this from your email administrator.
Additional information
Visit our Online Support Center to find common solutions.
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