From the Outlook Application:
https://support.microsoft.com/en-us/office/send-automatic-out-of-office-replies-from-outlook-9742f476-5348-4f9f-997f-5e208513bd67
From Outlook Web App:
https://support.microsoft.com/en-us/office/send-automatic-out-of-office-replies-in-outlook-on-the-web-0c193ab0-b9e1-4058-84be-a5b014242290