Is there an email client (if somebody knows how to do this in Gmail, also interested in that) that allows writing a mail, and sending it at a predefined time in the future? Say, I write a mail at 2 a.m. and the client (computer is always on) sends it at 8 a.m. the same day (while I'm most probably sleeping).
TrulyMail can easily do this (no add-ons required). Just compose the message and click Send Later and choose the time you want it to go out. It's free and quite easy to use.