I am not very familiar with the Delay Delivery feature in Outlook. Would a delayed delivery email send even if Outlook is closed and the computer off? I have not been able to find anything saying definitively that it would or would not send.
I think I recall that with older versions of Outlook and Exchange, Out Of Office messages only sent if the user's Outlook was open, and I wasn't sure if there was some restriction with delayed delivery messages and current versions of Outlook and Exchange.
The client is Outlook 2007, and the server is Exchange 2007.