Gmail and Yahoo mail have adverts in their online webmail to help pay for the service which they offer for free. But if you received Windows 10 with your computer you have paid for the OS since the OEM will have had to give MS a license fee to install it on the computer before it ships. And that included the mail client and so you should not be expected to have to put up with ads as well.
I would have some sympathy if a small developer had released an ads supported free email client to help pay for development costs and you could pay extra to have them removed. But not from a company that made $16bn profit.