You can set the task scheduler to run your mail client (Outlook, Outlook Express, whatever) at that certain time.
Write a mail draft and don't send it out. Configure your e-mail client to Send/Receive on start-up and that should do it.
There's no guarantee on when you'll get the actual e-mail, though. 😛 Takes me 20 minutes to send an e-mail to a friend
13 miles away at work and 2 minutes to send one to my brother in Oklahoma.