This:
"We noticed a mismatch that may prevent you from getting TSA PreCheck on your trip."
...showed up today.
It also advises me to " Go to
www.dhs.gov/tt, choose your Trusted Traveler program and log in." However, there is no log-in link on the page. I called TSA's press office and was told that this was a mass mailing by American, and that they'd (TSA) gotten a number of calls on it. She said everything's likely fine. I checked my pax info on the flight for tomorrow and all of it was correct. The KTN was XXXX-ed, as others on this thread have reported, which is as it should be. I called AA and the CSR confirmed that others have called about the email, and that they had also expressed frustration about no obvious (we may all be missing it somehow) log-in link on the TSA page. Since all looks good otherwise, the the thing to do is check my e-boarding pass tonight after OLCI for tomorrow's flight.
Updated after OLCI: No PreCheck symbol on BP. AA CSR says they've been hearing about it today. All my correct info is in my profile.