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Comcast DMARC Update

Comcast recently implemented the Domain-based Authentication, Reporting, and Conformance (DMARC) specification as a new way to help prevent phishing messages from reaching our customers’ mailboxes. DMARC enables a domain to publicly indicate (via DNS) what action should be taken for mail claiming to be from that domain that does not pass authentication and get reports about phishing and spam messages that did not come from approved mail servers.

Recent History
Recently, the policies that AOL and Yahoo published instructed mail servers that use DMARC to reject mail if it claims to be from or but failed authentication – meaning the mail did not originate from an approved mail server run by AOL or Yahoo, respectively. This has reportedly caused issues for some people using AOL or Yahoo addresses with email discussion lists and other mail sending tools. More information from AOL was posted here.

While AOL and Yahoo may be addressing spam and phishing issues in making this change, it does not yet appear to be typical DMARC usage. We have been asked whether Comcast plans to make similar changes soon, and we can confirm we have no such plans.

Comcast’s Future DMARC Plans
To help us improve our detection of those who use the domain maliciously we have published a DMARC record for, but that change WILL NOT disrupt legitimate messaging. This policy will not ask other services to reject messages that did not originate from us, but rather report those instances to us for research. We will also publish DMARC reject policies in the coming months for the domains used by our Xfinity Billing, Xfinity Home, and Customer Security Assurance notifications. These originate from specific domains and servers that we maintain. This will not negatively affect email discussion lists but will help us prevent some of phishing messages that might attempt to target our customers.

If You Have Been Negatively Affected by AOL’s and Yahoo’s Changes
If you are an Xfinity Internet customer, use an AOL or Yahoo email account regularly, and are having problems getting email from email discussion lists or other tools at those addresses, we invite you consider activating or using your email account.

To signup, add, or change your email account - Click Here

Once your email address is registered, you can access it in several ways:
For webmail users - Click Here
For email client users - Click Here
For mobile email users - Click Here