Hello Yousaaf8, you can remove addresses from the auto-complete list Windows 10 mail by opening Outlook, press on the Mail tab so you are see your mailbo and press on the option that says New Email. Press
https://appuals.com/remove-addresses-from-the-auto-complete-list-windows-10-mail-app/ this link to find more solutions. Here in the new e-mail window, start writing the address you need to remove in the To: field. When it pops up, tap the X button next to the address. If it doesn't work then you can remove the complete auto-complete list by opening Outlook, press on the File tab at the top of the screen and tap Options. Here in the "Outlook Options" window, just press the Mail tab and go down to the option that says "Send Messages" and tap on the Empty Auto-Complete List button.