Solve the Windows 10 Mail app error 0x8019019a issue, follow the steps below:

Access the Mail app by clicking on its icon either located on the Taskbar or Start menu.
Click on the gear icon to access the Settings menu of the Mail app.
Click Manage Accounts and select your Yahoo account.
Click Remove this account from this device and close the window.

Now, head over to your default browser and apply the following steps:
Sign in to your Yahoo Mail account using your existing login credentials.
Click on your name at the top-right and select Account info.
In the emerging session, choose Account security.
A new tab will appear. Look for Manage app passwords located at the bottom of the page and click on it.
Select Other app on the dropdown menu.
Click on the Generate button and the mail client will present a password with 16 characters. Copy it.
Now, the browser part is done.

You can head back to the Mail app and reopen it the same way you did earlier on. Once launched, apply the following steps:
Click on the gear icon to access the Mail app Settings window.
Select Manage accounts just like you did earlier and click on + to add an account.
Don’t choose Yahoo. Click on Other accounts (POP, IMAP) instead.
Now, insert your Yahoo email address.
When prompted to insert a password, paste the one you copied from your browser mail client with 16 characters.
Type in your username and click Save.

Using this method to add a Yahoo account has helped a lot of users prevent the Windows 10 Mail app error 0x8019019a issue. It should help solve your issue as well. Just be sure to follow the instructions as outlined.
(If problem persist, do a COMPLETE virus scan and then these steps again)

Yeah do I look like a fucking Yahoo?

Only if you can't get your email to work ...

Never tried, I did use outlook express long ago.

Was that Michael Richards?

That's Yahoo Serious ...
(Young Einstein)