Using New Outlook on Windows for personal email, calendar, and contact management
Just used this method with help from ChatGPT....
Open the Sent Email: Locate the email you want to duplicate in the Sent Items folder.
In the Ribbon Bar, Under "Move" Grouping click on the "Actions" button (sometimes labeled as Move or with three dots depending on your version).
Select "Resend This Message":
This opens the email as if you're resending it.
Edit the Email:
Make any changes you want.
Send or Save as Draft:
Either send it immediately or save it as a draft for later.