As a serial entrepreneur that is the brains in building the entire hardware and software of several acquired systems I have been the recipient of multiple such certified delivery cease and desists. While my case does not match that of this topics point mine was threating to inform me to stay out of the industry which clearly I did not, just a scare tactic without grounds because they knew of my talents. My most recent exit I secured a legally binding document with the new owner that states I cannot be pursued for anything by either the parent company or any future subsidiary. It has been crickets.
As others say your best option is to read and understand your situation since you lived it as no one will care more about it than you, not even a lawyer you are paying but they will gladly take your money, again from experience.
As a serial entrepreneur that is the brains in building the entire hardware and software of several acquired systems I have been the recipient of multiple such certified delivery cease and desists. While my case does not match that of this topics point mine was threating to inform me to stay out of the industry which clearly I did not, just a scare tactic without grounds because they knew of my talents. My most recent exit I secured a legally binding document with the new owner that states I cannot be pursued for anything by either the parent company or any future subsidiary. It has been crickets.
As others say your best option is to read and understand your situation since you lived it as no one will care more about it than you, not even a lawyer you are paying but they will gladly take your money, again from experience.