Microsoft is adding support for sending emails via alias email addresses (also known as aliases or proxy addresses) Microsoft is planning to make this new feature available worldwide in standard multi-tenant environments by the end of next month. Users will be able to choose the sender or FROM address via a drop-down list within the email compose pane. The alias email address will be preserved in the FROM and REPLY TO for the recipients. The company is also planning to roll-out support for disposable emails to Exchange Online in October 2020.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-outlook-for-windows-will-let-you-send-emails-from-aliases/