Summary
Comcast 'no mail servers could be reached' timeout issues stem from a confluence of factors including temporary DNS errors, DNS propagation delays, incorrect DNS records, firewall configurations blocking SMTP, recipient server issues, Comcast's servers being blacklisted, and internal Comcast issues. Resolution involves checking DNS settings and records, monitoring blacklists, reviewing firewall logs, contacting Comcast support, retrying the email, and contacting the recipient directly. Specific timeout IPs 96.114.157.80 and 68.87.20.5 have been noted, and Comcast typically requires around 7 hours to resolve such issues.
Key findings
- DNS Issues: Transient DNS errors, DNS propagation delays, and incorrect DNS records are common causes.
- Firewall Problems: Firewall settings may be blocking SMTP ports, preventing email delivery.
- Blacklisting: Comcast's servers could be blacklisted, causing delivery failures.
- Recipient Issues: The recipient's mail server may be down for maintenance or experiencing problems.
- Comcast Internal Issues: Comcast may be experiencing internal network issues or outages affecting email services.
- Timeout IPs: Specific IPs 96.114.157.80 and 68.87.20.5 are associated with timeouts.
- Resolution Time: Comcast generally needs ~7 hours to resolve issues with mail servers
Key considerations
- Check DNS: Verify DNS server configuration and ensure proper DNS records (A, MX, TXT).
- Monitor Blacklists: Check if Comcast's IPs are on any common blacklists.
- Review Firewalls: Ensure firewalls are not blocking SMTP ports.
- Contact Comcast: Contact Comcast support for detailed insights into outages or network issues.
- Retry Email: Try resending the email after a delay.
- Contact Recipient: Contact the recipient through an alternate method to confirm delivery.
- Use Diagnostic Tools: Use tools like MXToolbox for DNS and blacklist checks.
What email marketers say
13 marketer opinions
Comcast 'no mail servers could be reached' timeout issues can be caused by a variety of factors, including temporary DNS resolution problems, Comcast's outbound mail servers being blacklisted, firewall issues, recipient mail server issues, incorrect DNS records, or DNS server outages. Resolution involves checking DNS server configurations, monitoring for blacklisting, reviewing firewall logs, and contacting Comcast support for detailed insights. Retrying the email later or contacting recipients directly are also advised.
Key opinions
- DNS Issues: Temporary DNS resolution problems, incorrect DNS records, or DNS server outages on either the sending (Comcast) or receiving side can lead to timeout errors.
- Blacklisting: Comcast's outbound mail servers may be temporarily blacklisted, preventing successful email delivery.
- Firewall: Firewall issues can block connections between Comcast's servers and recipient mail servers.
- Recipient Server Issues: Issues with the recipient's mail server, such as maintenance or outages, can cause undeliverable errors.
- Timeout IPs: Timeout issues seen with IPs 96.114.157.80 & 68.87.20.5
- Resolution Times: Comcast have had issues with resolution and it has taken around 7 hours to resolve
Key considerations
- Check DNS: Verify DNS server configurations and ensure proper DNS record settings.
- Monitor Blacklists: Use online tools to check if Comcast's IPs are blacklisted.
- Review Firewalls: Examine firewall logs to identify and resolve any blocking rules.
- Contact Comcast: Contact Comcast support for specific insights into outages or network problems.
- Retry or Contact Recipient: Try resending the email later or contact the recipient through an alternative method.
- Bounce Response Monitoring: Monitor bounce responses for timeout issues.
Marketer view
Marketer from Email Geeks confirmed that those IPs are not backup MX records.
4 Oct 2024 - Email Geeks
Marketer view
Marketer from Email Geeks shares they're seeing increases in timeouts, tens of thousands in the last hour.
24 Nov 2023 - Email Geeks
What the experts say
2 expert opinions
Comcast 'no mail servers could be reached' timeout issues are often attributed to temporary DNS problems, server maintenance, recipient mail server problems, or Comcast's IP address being blacklisted. Resolution involves retrying the email, contacting the recipient through alternative channels, or checking common blocking lists to see if Comcast's server is listed.
Key opinions
- DNS Issues: Temporary DNS issues can prevent mail servers from being reached.
- Server Maintenance: Scheduled or unscheduled server maintenance on either the sending or receiving end can cause temporary outages.
- Blacklisting: If Comcast's IP is blacklisted, email delivery will be blocked.
- Recipient Issues: Problems with the recipient's mail server may cause the error message.
Key considerations
- Retry Email: Try sending the email again after a short delay.
- Contact Recipient: Contact the recipient via an alternative method to confirm delivery.
- Check Blocking Lists: Check if Comcast's IP is on any common blacklists.
Expert view
Expert from Word to the Wise explains that bounce messages like 'no mail servers could be reached' can occur due to temporary DNS issues, server maintenance, or problems with the recipient's mail server. Retrying the email or contacting the recipient through an alternate method is advised.
2 Mar 2022 - Word to the Wise
Expert view
Expert from SpamResource explains that issues often happen when email providers find you on a blocking list. If your email provider (Comcast in this case) gets blacklisted, emails can get blocked which would produce the type of error. They suggests checking common blocking lists to check if the sending server is listed.
16 Apr 2025 - SpamResource
What the documentation says
5 technical articles
Comcast 'no mail servers could be reached' timeout issues are often caused by transient DNS errors, DNS propagation delays, or incorrect DNS records. Firewall settings blocking SMTP ports can also be a factor. Resolution involves checking DNS configurations, verifying DNS records (A, MX, TXT), allowing time for DNS propagation, and utilizing tools like MX Lookup, DNS Lookup, and Blacklist Check to diagnose the root cause. Checking firewall settings is also recommended.
Key findings
- Transient DNS Errors: The error often indicates temporary DNS issues that may resolve automatically.
- DNS Propagation Delays: Delays in DNS propagation after changes can cause the error.
- Incorrect DNS Records: Improperly configured DNS records (A, MX, TXT) can lead to delivery problems.
- Firewall Settings: Firewall settings blocking SMTP ports can prevent successful email delivery.
Key considerations
- Check DNS Configuration: Verify DNS server configurations and settings.
- Verify DNS Records: Double-check A, MX, and TXT records for accuracy.
- Allow DNS Propagation: Allow sufficient time for DNS changes to propagate globally.
- Use Diagnostic Tools: Utilize tools like MX Lookup, DNS Lookup, and Blacklist Check to identify issues.
- Check Firewall Settings: Ensure firewall settings are not blocking SMTP ports.
Technical article
Documentation from Microsoft Learn explains that 'no mail servers for domain could be reached' often indicates transient DNS errors. These are often temporary and resolve automatically when DNS infrastructure corrects itself. The documentation suggests checking DNS server configuration and waiting for propagation after changes.
25 Mar 2023 - Microsoft Learn
Technical article
Documentation from Google Workspace Admin Toolbox explains one of the most common reasons is firewall settings. The firewall may be blocking the port that SMTP usually connects to. Checking the connection is necessary to find the root cause, which will help narrow down the next steps to resolve it.
17 Jul 2024 - Google Workspace Admin Toolbox
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