Future Me - Send an email to your future self
Letter to Yourself - Send a physical letter to your future self
Incubate - Time-delay messaging app
Letterflix - Send letters and snail mail online to the USA, Europe, India, or anywhere in the world. Letterflix is the easiest and secure way to send letters and snail mail anywhere in the world from the comfort of your home.
Vuash - Send secret messages safely.
Modern Memories - Letters written today. Delivered in the future.