If you have a Standard, it will not be accepted as proof of identification to board a domestic flight after October 1, 2021 unless you have a Passport.
how can I get an ID card by mail?
You will need a a completed Application for Permit, Driver License or Non-Driver ID Card and your license must be current or expired for less than 2 years.   You will also need a photocopy of your proof that you receive SSI, and you will need to send in payment.