You can delay the delivery of an individual message or you can use rules to delay the delivery of all messages by having them held in the Outbox for a specified time after you click Send.
Delay the delivery of a message
1. While composing a message, select the More options arrow from the Tags group in the Ribbon.
2. Under Delivery options, select the Do not deliver before check box, and then click the delivery date and time you want.
3. Click Close.
4. When you're done composing your email message, select Send.
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:
1. Switch to the Outbox folder.
2. Open the delayed message.
3. Select the More options arrow from the Tags group in the Ribbon.
Under Delivery options, clear the Do not deliver before check box.
Click Close and send.
Note: This feature works only when Outlook is in online mode.