Yes you can, it's especially easy if you connect to an Exchange server. Do
you?
In the open email that you're composing, click on Options. Check the box "do
not deliver before" and then set the time. Click Send after you're finished
composing the mail. It will sit in your Outbox. Exchange will send the email
for you at the right time.
If you're using a different type of account, you'll have to leave Outlook on
and running at the time you want the email to go out.
