Followup.cc - FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.

Future Me - Send an email to your future self

Gmelius - Gmelius is the first collaboration platform designed for G Suite and your company's daily tools.

Letter to my future self - Letter to my future self is a prominent email scheduling service that gives you the opportunity to create a letter with goals and thoughts for your future self and schedule a date for sending it.

FollowUpThen - The simplest way to schedule an email reminder

Letter to Yourself - Send a physical letter to your future self