Open Outlook and click New Email
Compose your message
Select the Options tab
Click Delay Delivery
Check Do not deliver before
Set the date and time you want the email sent
Click Close
Click Send
Keep Outlook open until the email is sent, or make sure you are using an Exchange or Microsoft 365 account that supports server-side delivery
For Outlook on the web, compose the email, click the arrow next to Send, choose Send later, set the date and time, and click Send