Open Outlook and start a new email
Go to the Options tab
Select Delay Delivery
Check Do not deliver before
Choose the date and time you want the email sent
Click Close
Click Send
Keep Outlook open until the message is sent, or make sure it is connected to the server if using Outlook on the web or Exchange rules
To delay all outgoing emails, go to File
Select Manage Rules & Alerts
Create a new rule
Apply the rule to all messages you send
Choose defer delivery by a number of minutes
Set the delay time
Save the rule