Yahoo! mail account users who are using a Windows 10 PC need to use either a web browser or an unofficial email client to check emails. Luckily, the default Windows 10 Mail app supports Yahoo! Mail as well. One can add Yahoo! Mail account to Windows 10 Mail app with a few clicks.
Follow the given below directions to add your Yahoo! Mail account to Windows 10 Mail app.
Add Yahoo! Mail to Windows 10 Mail app
Step 1: Launch the Mail app. Click the Settings (gear) icon in the lower left-pane to open Settings.
Step 2: Click Manage Accounts.
Step 3: Click Add account. This action will open a page with all top webmail providers, including Yahoo!.
Step 4: Click Yahoo! option. You should now see the Yahoo! Mail sign in page.
Step 5: Type in your Yahoo! Mail email address. Click Next button.
Step 6: Next, enter your Yahoo! Mail account password. Click Sign in button.
Step 7: If you have enabled two-step verification for your Yahoo! account, you will see the following screen where you can select a method to verify your account. Select one of the methods, click Verify to receive the verification code. Enter the code you received on your phone or email to complete the verification.
Step 8: When you see the following page, click Agree button to allow the Mail app to access your Yahoo! account contacts, profiles, and calendar.
Step 9: If you see the following screen with “Let Windows remember your sign-in name and password so you don’t have to” message, click Yes button. That’s it!
You should now see “All done! Your account was set up successfully” message. Click Done button.
The Mail app will start syncing your emails.
Also check out how to add Gmail account to Windows 10 Mail app.
Source: http://www.intowindows.com/how-to-add-yahoo-mail-account-to-windows-10-mail/
