Summary
During peak sending periods, such as Cyber Monday, email delivery to major internet service providers (ISPs) like Comcast can experience significant delays. This thread highlights a real-world scenario where senders encountered SMTP connection timeouts and emails queuing up, rather than bouncing, indicating a slow but ongoing delivery process.
Key findings
- Widespread delays: Multiple senders confirmed experiencing slow email delivery to Comcast on Cyber Monday, with SMTP connection issues reported.
- Queuing not bouncing: Emails were observed to be queuing and delivering very slowly, rather than being rejected outright, suggesting system congestion.
- Similar issues elsewhere: Yahoo and AOL were also noted to be slower than normal, reinforcing the idea of a broader industry-wide stress point during high volume events.
- ISP acknowledgement: A Comcast representative confirmed that changes were being implemented to help address the issues, with an expectation of a backlog clearing.
Key considerations
- Peak season preparation: Anticipate increased load and potential throttling during major sending holidays.
- Monitoring vital: Actively monitor your email queues and delivery logs, particularly for connection timeouts or excessive delays to specific domains. For more on this, see why your emails are delayed.
- ISP communication: Stay informed through postmaster pages, community forums, or direct contacts for major ISPs. Comcast users sometimes experience delays. The Xfinity Community Forum discusses these.
- Backlog management: Understand that even after issues are addressed, a backlog of mail can take time to clear, impacting real-time campaign performance.
What email marketers say
Email marketers widely report that Cyber Monday, and the broader holiday shopping period, often presents significant challenges for email deliverability. This year was no exception, with many experiencing direct impact on their campaigns due to slow mail flow to major inbox providers, particularly Comcast. The shared frustration underscores the need for proactive strategies to navigate high-volume sending events.
Key opinions
- Shared experiences: Multiple marketers quickly confirmed the slow delivery issues to Comcast, indicating a shared, rather than isolated, problem.
- Peak volume suspected: The common assumption among marketers was that the delays were due to extremely high mail volume overloading ISP systems.
- Cross-ISP impact: Observations extended beyond Comcast, with Yahoo and AOL also showing signs of slower delivery, suggesting broader system strain.
- Business impact: Marketers expressed concern over the delays impacting critical Cyber Monday campaigns, where timely delivery is essential for conversions.
Key considerations
- Community insights: Leveraging communities like Email Geeks or public forums can provide rapid confirmation of widespread issues, helping to differentiate between individual sender problems and broader ISP challenges.
- Strategic sending: Consider adjusting sending schedules or breaking down large sends during peak periods to mitigate the impact of potential throttling. Learn more about Comcast email throttling.
- Performance monitoring: Implement robust monitoring for deliverability to key domains, allowing for quick identification of slowdowns. Use an email deliverability test.
- Customer service impact: Delays can lead to increased customer service inquiries. The GetHuman Comcast customer service archive shows these types of issues.
Marketer view
Marketer from Email Geeks observed significant email delivery delays to Comcast on Cyber Monday. They noted that SMTP tests were failing to connect to Comcast's mail exchange servers, specifically mx1.mxge.comcast.net and mx2.mxge.comcast.net, after 15 seconds.Mail started queuing up around 7:00 AM Eastern time, and has since been delivering very, very slowly, but importantly, not bouncing.
Marketer view
Marketer from Email Geeks confirmed experiencing identical slow delivery issues to Comcast. This quick corroboration indicated that the problem was not isolated to a single sender, but was a more widespread phenomenon affecting multiple parties.The shared observation highlighted the systemic nature of the delivery slowdown on that particular day.
What the experts say
Email deliverability experts highlight that periods of exceptionally high email volume, such as Cyber Monday, place immense strain on ISP infrastructure. While not always visible as outright bounces, this stress can manifest as significant delivery delays and queuing. The direct communication from a Comcast expert in this instance provides valuable insight into the internal measures taken by ISPs to manage such loads.
Key opinions
- Internal adjustments: A Comcast expert confirmed that internal changes were made to alleviate the observed delivery slowdown.
- Expected backlog: Despite implemented changes, an expert anticipated a backlog of emails would still need time to clear.
- System resilience: High volume events test the robustness of email infrastructure, sometimes leading to temporary queuing mechanisms rather than outright rejections.
- Dynamic throttling: ISPs often employ dynamic throttling to manage inbound queues and protect their systems during traffic spikes, which results in slower delivery for senders.
Key considerations
- ISP capacity: Recognize that even the largest ISPs have capacity limits, and extreme peak periods can push these limits, causing delays. For more information, read how to resolve Comcast email issues.
- System adjustments: Understand that ISPs are continuously making adjustments to handle volume, and sometimes these changes can temporarily impact delivery speed. This is part of general email deliverability issues.
- Queue management: If you observe persistent queuing to a specific ISP, it may indicate a need to adjust your sending rate or segment your audience for that domain.
- Proactive monitoring: Leverage tools and community discussions to stay ahead of known or anticipated deliverability challenges during critical sending windows, as suggested by experts at SpamResource.com.
Expert view
Expert from Email Geeks (Comcast representative) confirmed that internal changes were made to address the observed delivery slowdowns. This indicates that Comcast was aware of the issue and actively working to resolve the congestion affecting email flow.Such direct acknowledgment from an ISP is crucial for senders seeking clarity during deliverability challenges.
Expert view
Expert from Email Geeks (Comcast representative) also acknowledged that despite the implemented changes, a backlog of emails was still expected. This implies that while the immediate cause of the slowdown might be mitigated, the sheer volume of queued mail would take time to process and deliver fully.It highlights the lag between issue resolution and full service recovery for high-volume systems.
What the documentation says
Official documentation and technical resources often outline the complexities of large-scale email systems and internet infrastructure. While specific details on real-time service disruptions like the Cyber Monday Comcast delays are rarely public, documentation provides insights into how ISPs manage traffic, potential causes of slowdowns, and troubleshooting steps that can be inferred. This includes system-level optimizations and general network health.
Key findings
- Sorting order awareness: Xfinity community forums sometimes suggest checking email sorting order as a basic troubleshooting step for not seeing new emails, implying user-side issues can mimic delivery delays.
- Latency reduction technology: Comcast is rolling out technology like L4S, designed to reduce network latency, which could indirectly improve the responsiveness of email delivery.
- General troubleshooting guides: Comprehensive guides exist for diagnosing and fixing slow internet connections with Xfinity, covering various potential causes that might affect email.
- Basic network fixes: Simple actions like restarting routers or optimizing their location are often cited as ways to improve Xfinity internet speeds, which can impact email services.
Key considerations
- Holistic troubleshooting: While email-specific issues are common, broader network performance issues can also contribute to perceived email delays. Consider how greylisting might impact email delivery.
- ISP infrastructure upgrades: ISPs continually upgrade their network infrastructure, with new technologies aimed at improving speed and reliability. These efforts generally enhance overall service, including email delivery, as discussed in technical solutions from top senders.
- Understanding network limitations: Even with advanced technology, network congestion during peak times is a fundamental challenge. General guides like those on HighSpeedInternet.com provide insight into various factors affecting internet speed.
- Reliance on external factors: Email deliverability is often dependent on the underlying stability and performance of broad internet infrastructure, not just mail servers.
Technical article
Documentation from Xfinity Community Forum advises users experiencing issues with seeing new emails to first check their email sorting order. It specifically asks if the sorting order is set to date and descending. This highlights a common user-side troubleshooting step.It suggests that sometimes perceived delivery issues are due to how emails are displayed rather than actual delays.
Technical article
Documentation from The Verge highlights Comcast's adoption of L4S technology, designed to reduce network latency. This new standard aims to significantly improve responsiveness for applications like video games.While not directly about email, reduced network latency can indirectly benefit email transfer speeds by improving the overall efficiency of data transmission across Comcast's network.
Related resources
8 resources
Related pages
How to prevent email throttling and delays from Hotmail, Comcast, and other email clients?
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What causes Comcast email throttling and how can I improve my open rates?
How to resolve Comcast email rejections and throttling issues?
Why are my emails delayed even with a good reputation and no errors?
Understanding email greylisting and how it works
Email Deliverability Issues: Getting Your Messages to the Inbox in 2025
Boost Email Deliverability Rates: Technical Solutions from Top Performing Senders
How to Run an Email Deliverability Test: A Proven Checklist
Why Your Emails Fail: Expert Guide to Improve Email Deliverability [2025]
