You haven't posted enough information to be sure, but the message was received by email, it's probably a phishing scam, an attempt to steal login and account information. If you check your email with Comcast's Xfinity Connect webmail, look for the XFINITY Verified Email logo next to any message that claims to be from Comcast/Xfinity (see https://www.xfinity.com/support/articles/comcast-verified-email).
Please see Comcast Email Phish or Legit? How to Tell (and rules for posting) for more information about identifying phishing emails. The article is somewhat out of date, but still useful.
Samples of recent phishing messages can be found at http://constantguard.comcast.net/help/alerts under "Top Phishing Scams".
@weems2267 wrote: Why did I get a message that you have the right to delete my email??????
If you got a notice about Comcast's new Email Activity Policy, see https://www.xfinity.com/support/articles/email-activity. In Comcast's Customer Agreement (see https://www.xfinity.com/Corporate/Customers/Policies/SubscriberAgreement) they reserve the right to make any changes they want, any time they want. The Agreement protects them, not you.
Why would they impose this new burden on their customers? Ultimately because it saves them money, and therefore increases their profits. And perhaps they are afraid to lose their honored status as Most Hated Company In America?