Advanced SecurityHaving trouble accessing any websites using a compatible xFi Gateway.How can we help?
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Advanced SecurityHaving trouble accessing any websites using a compatible xFi Gateway.
Email AbuseIf you are receiving spam, harassing, phishing, or unwanted emails.
Identity TheftYour personal information was used by Comcast without your authorization.
Network AbuseExperiencing online harassment or issues with network security.
PostmasterIf you're having an issue with sending or receiving E-Mail with Comcast.Frequently Asked Questions
What do I need to know to avoid blocks when sending to Comcast?
1. Conform to the standards
All email must comply with all relevant RFCs.
2. Ensure your rDNS is correct
Comcast performs an rDNS check on the IP of the sending server. If the sending server does not have a PTR record and a MX or an A record set up properly, the connections will not be accepted.
3. Stay off DNSBL lists
Comcast consults several DNSBLs including Spamhaus Zen, and ReturnPath. Being listed on any reputable, widely used, DNSBL is likely to cause your email to be blocked not only by Comcast, but other ISPs as well.
4. Keep your distribution lists clean
A large number of undeliverable emails sent to Comcast will result in a sending IP being blocked. All “Not Our Customer” NDNs should be treated as an unsubscribe request.
5. Practice good abuse management
Enforce AUPs and mitigate compromised accounts and machines. Dictionary or Directory Harvest attacks are treated seriously and will quickly lead to the sending IP being blocked.
6. Keep it Static
Dynamic IP space is a common haven for compromised machines used in bot networks. As a result, in keeping with industry best practices, Comcast does not accept mail from dynamic IP space. If email appears to be coming from dynamic IP space then it will not be accepted.
7. Keep your IP reputation clean
Overall IP reputation is key to successfully sending to Comcast. If Comcast, or another reputable organization repeatedly receives spam, spyware or other malicious attacks, phishing efforts or other deceptive emails from a certain IP address, Comcast is more likely to block future messages from that IP address. Ensure the overall sending reputation of the sending mail system is as clean as possible.
8. Pay attention to error messages
Most non-delivery notifications Comcast returns contain links to FAQs which explain why the block occurred and instruct in how to remediate the issue. Take the time to review any errors; it is likely they hold the key to a quick remediation.
Visit our error messages page.
9. Watch the sending limits
Comcast allows 25 simultaneous connections per sending IP address.
Comcast allows 100 recipients per message.
Comcast allows a throttle rate based on your sender reputation and authentication.
What do I need to know to avoid blocks when sending to Comcast over IPv6?
What are Comcast's Outbound Mail Servers?
What are Comcast's mail delivery error messages?
What are Comcast's Dynamic IP Ranges?
How do I get my IP block removed?
How do I sign up for Comcast's feedback loop?
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