Update 1: 2018/08/23 8:52pm PDT
According to a comment by a T-Mobile employee on the Reddit post only government, business or accounts with 100+ lines will receive letters.
Some T-Mobile customers may be receiving a message in the coming days regarding a security incident which took place on August 20th. According to the notice received by some customers already, "certain information" including names, addresses, account numbers, and account types may have been accessed in the breach before unauthorized access was shut down.Read More
T-Mobile is notifying some customers about a recent security breach was written by the awesome team at Android Police.