[jrockway]

This is easy enough to do on a UNIX machine. Compose your message, then delay the sending with at:

    $ at 8:00am sh -c 'mail [e-mail] < my_message.txt'

[attack]

Unless you want to delay it until birthdays or some other event that's weeks or months away.

[jrockway]

at lets you specify dates as day/month/year. All you have to do is make sure the computer is running at that time, which is easy if you do this on your mail server.

[attack]

That I know. I would never depend on a command line command to execute something months from now. Not on any system.