Roundcube - Web-based IMAP email client
Future Me - Send an email to your future self
HEY - Email at its best, new from Basecamp.
Dabble Me - Your own private place to write. A journal/diary to help you remember what's happened in your life.
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
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.