Microsoft's Outlook for Windows will soon allow you to send email from an account alias

If you want to use a new email address with your existing Outlook.com account, you can create one using account alias feature in Outlook.com. An alias uses the same inbox, contact list, and other account settings as your primary email address. You can even sign in to your Outlook.com account with any alias using the same primary email account password.

Microsoft recently confirmed that Outlook for Windows will soon have the ability to send email from a proxy email address or account alias rather than your primary email address. The alias email address will be preserved in the FROM and REPLY TO for the recipients. Microsoft will roll out this feature in March 2021.

Source: Microsoft