In the message, click Options.
In the More Options group, click Delay Delivery.
Under Delivery options, select the Do not deliver before check box, and then click the delivery date and time that you want.
After you click Send, the message remains in the Outbox folder until the delivery time.
If you decide later that you want to send the message immediately, do the following:
In Mail, in the Folder Pane, click the Outbox folder.
Open the delayed message
Click Options.
In the More Options group, click Delay Delivery.
Under Delivery options, clear the Do not deliver before check box.
Click Close.
Click Send.