Privacy Policy
Think Later is storing a hashed version of your username, along with the display name etc, on the device.
When a thought is saved, metric data containing the event and a value whether you send to your current account's email or another email-address, is sent to Mixpanel, which is used to follow up the activity of the app.
Mixpanel store some user meta data as well for user uniqueness, which is tied to the device and not your user account
Thoughts sent via Think Later is not stored in any Sent Mail folder, so only the reveiver which will have a copy of it.