Summary
Addressing Comcast throttling and deferral errors requires a multifaceted approach. It's crucial to reduce sending speeds and limit connections to Comcast's infrastructure, respecting their established thresholds for sending volume. While RL000003 throttling allows for retries, avoid overwhelming their servers. Understand that Comcast's throttling is based on historical sending quality and quantity. Maintain a clean email list, segment your audience, personalize messages, and gradually warm up new IPs. Focus on monitoring your sending reputation, implementing feedback loops with Comcast, and ensuring proper email authentication (SPF, DKIM, DMARC). Contact Comcast support directly for policy clarifications and potential whitelisting. Analyzing server logs, and employing deliverability monitoring tools can help identify specific issues. Treat deferrals as red flags indicating potential problems with sender reputation or exceeded sending limits. Regularly check your IP against blocklists and follow delisting procedures if necessary. Remember that Comcast is known to aggressively block email, making proactive communication and reputation management essential.
Key findings
- Sending Limits: Exceeding Comcast's sending volume thresholds triggers throttling.
- Historical Reputation: Comcast bases throttling on historical sending quality and quantity.
- Clean Lists: Maintaining a clean and engaged email list improves sender reputation.
- Authentication: Proper email authentication (SPF, DKIM, DMARC) is crucial for deliverability.
- Active Monitoring: Monitoring your sending reputation and deliverability is essential.
- Comcast Blocking: Comcast is known to aggressively block emails.
- Temporary Failures: SMTP 421 errors indicate temporary delivery failures requiring retries.
Key considerations
- Rate Limiting: Reduce sending rates and limit concurrent connections.
- Retry Strategy: Implement a retry strategy for deferred emails.
- List Hygiene: Regularly clean your email list to remove inactive or unengaged subscribers.
- Authentication Setup: Configure and maintain SPF, DKIM, and DMARC records correctly.
- Feedback Loops: Implement and monitor feedback loops with Comcast.
- Contact Comcast: Contact Comcast support to understand their policies and request whitelisting.
- Blocklist Monitoring: Check your IP address against blocklists and take action to delist if necessary.
- Server Logs: Analyze server logs for specific error details from Comcast.
What email marketers say
9 marketer opinions
To address Comcast throttling and deferral errors, email marketers should focus on several key areas. First, understand that Comcast's throttling (RL000003) is primarily volume-based, allowing for aggressive retries within minutes, but avoid overwhelming their servers. Comcast's throttling considers historical sending quality and quantity. Maintaining a clean email list, segmenting audiences, personalizing messages, and warming up IPs are crucial. Monitor your sending reputation, implement feedback loops with Comcast, and adhere to email authentication best practices (SPF, DKIM, DMARC). Contact Comcast support directly to inquire about policies and potential whitelisting. Analyze server logs for specific error details and consider employing tools to monitor deliverability. Treat deferrals as signals to review your email program for issues like poor sender reputation or exceeded sending limits.
Key opinions
- Volume-Based Throttling: Comcast's throttling is primarily based on sending volume, allowing for retries, but avoid overwhelming their servers.
- Historical Data: Comcast throttling decisions are based on historical sending quality and quantity.
- Reputation Matters: Maintaining a good sender reputation is critical to avoid throttling and deferrals.
- Authentication is Crucial: Adhering to email authentication best practices (SPF, DKIM, DMARC) helps minimize throttling.
- Active List Management: Routinely remove inactive users from your mailing lists to improve engagement rates.
Key considerations
- Sending Volume: Reduce sending rates and limit concurrent connections to avoid exceeding Comcast's thresholds.
- Retrying Deferrals: Retry deferrals within a few minutes, but avoid overwhelming Comcast's servers.
- Contact Comcast: Contact Comcast support directly to inquire about their specific policies and potential whitelisting options.
- Monitor Deliverability: Use tools to monitor your deliverability and identify potential issues promptly.
- Server Logs Analysis: Analyze server logs for specific error details from Comcast to diagnose issues.
Marketer view
Marketer from Email Geeks shares that notes on RL000003 are that it can be retried pretty aggressively and not something impactful to deliverability since it's purely a volume based rate limit.
16 Mar 2024 - Email Geeks
Marketer view
Email marketer from Reddit shares that Comcast Business Class sometimes has aggressive filtering and that contacting Comcast support directly to whitelist your sending IP can help resolve delivery issues.
3 Nov 2024 - Reddit
What the experts say
3 expert opinions
To address Comcast throttling and deferral errors, experts recommend adjusting sending practices and actively investigating potential issues. You should reduce sending speeds and limit the number of connections to Comcast's infrastructure. Given Comcast's reputation for aggressive blocking, contacting them directly to understand their policies is advised. Checking your domain and IP reputation using various tools and ensuring proper email authentication (SPF, DKIM, DMARC) is crucial. Also, leverage feedback loops to understand what Comcast is specifically reporting about your mailings.
Key opinions
- Sending Speed Matters: Reducing sending speed and limiting connections can mitigate throttling.
- Direct Communication: Direct contact with Comcast is valuable due to their known blocking practices.
- Reputation Monitoring: Checking domain and IP reputation is critical for identifying potential deliverability issues.
- Email Authentication: Proper email authentication (SPF, DKIM, DMARC) is essential.
- Feedback Loop Analysis: Feedback loops provide insights into Comcast's specific concerns about your mailings.
Key considerations
- Infrastructure Adjustment: Make necessary adjustments to your sending infrastructure to comply with Comcast's requirements.
- Policy Understanding: Thoroughly understand Comcast's email sending policies.
- Proactive Monitoring: Implement proactive monitoring of your domain and IP reputation.
- Authentication Verification: Verify that your email authentication is correctly configured.
- Feedback Loop Integration: Integrate feedback loop data into your deliverability strategy.
Expert view
Expert from Email Geeks explains the user is being told that they need to send slower and limit the number of connections they're making to Comcast's infrastructure.
14 Jan 2024 - Email Geeks
Expert view
Expert from Word to the Wise, Laura Atkins, suggests checking your domain and IP reputation by using various tools, and also making sure to authenticate your emails. Also check feedback loops to see what Comcast is saying about your mailings.
15 Sep 2023 - Word to the Wise
What the documentation says
4 technical articles
According to official documentation, Comcast throttling (RL000003) signals that your sending volume surpasses established limits, advising a reduction in sending rates and concurrent connections. An SMTP 421 error code indicates a temporary failure, necessitating deferred sending and subsequent retries. To avoid deferrals, it's critical to verify sender reputation, ensure your IP isn't blacklisted, and confirm proper configuration of email authentication (SPF, DKIM, DMARC). Checking your IP address against blocklists and pursuing delisting if necessary is also crucial.
Key findings
- Volume Limits: Comcast throttling indicates exceeded sending volume thresholds.
- Temporary Failure: SMTP 421 errors denote temporary delivery failures requiring retries.
- Reputation Impact: Sender reputation directly impacts email deferrals.
- Authentication Importance: Correct email authentication (SPF, DKIM, DMARC) is vital for deliverability.
- Blocklist Monitoring: IP address blocklisting affects email deliverability.
Key considerations
- Rate Reduction: Reduce sending rates and concurrent connections when throttled.
- Retry Strategy: Implement a retry strategy for emails that receive 421 errors.
- Reputation Management: Actively manage and monitor your sender reputation.
- Authentication Setup: Verify and maintain correct SPF, DKIM, and DMARC configurations.
- Blocklist Checks: Regularly check IP addresses against blocklists and follow delisting procedures when needed.
Technical article
Documentation from Spamhaus explains that checking your IP address against blocklists is crucial. If your IP is listed, follow the delisting procedures outlined by the blocklist provider to improve deliverability and reduce deferrals.
2 Nov 2023 - Spamhaus
Technical article
Documentation from Comcast Postmaster Website explains that throttling (RL000003) indicates that your sending volume has exceeded established thresholds. They recommend reducing sending rates and the number of concurrent connections.
8 Mar 2022 - Comcast Postmaster Website
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