Using kmail 5.2.3 on debian9
I'm having problems setting up a new imap account in kmail using an existing yahoo account.
In kmail settings, I've set up a new identity and a new account; I don't see any folders in serverside subscriptions, but the new account shows as ready in the account list.
There are no folders created for the new account, no inbox, no evidence that it exists, other than in settings.
Following other threads, I looked in Akonadi Console - the new account appears in the agents tab, but not under collections in the browser tab.
Is there something special about yahoo? I set up an imap account with a different email provider in an earlier version of kmail without any problem which works fine. What am I missing?

Solved:
use imap.mail.att.net
use plain for login
set yahoo to accept less secure logins

When attempting to setup a imap Yahoo account I get the following error message:

The server for account "My Yahoo! Account" refused the supplied username and password.
Do you want to go to the settings, have another attempt at logging in, or do nothing?

Login failed, server replied: A000002 NO AUTHENTICATE Invalid credentials [ AUTHENTICATIONFAILED ]

The username and password are correct. Any ideas on how to resolve this?

Here is updated email settings

Incoming Mail Server
Account Type: IMAP
Username: Your email address is your username
Server hostname: imap.mail.att.net
Server port: 993
Authentication: Password
SSL/TLS: Yes

Outgoing Mail Server
Account Type: SMTP
Username: Your email address is your username
Server hostname: smtp.mail.att.net
Server port: 465
Authentication: Password
SSL/TLS: Yes

Link removed by moderator

Thx coolpintud. One more questions. You said to use "Authentication: Password", however Kmail does not give me "Password" as an option. Below are the options I'm given. Should I choose one of those?

LOGIN
PLAIN
CRAM-MD5
DIGEST-MD5
NTLM
GSSAPI
XOAUTH2

use PLAIN

and!

generate a so named "App-Password" in Security Settings within your Yahoo Profil

use this generated App-Password with your regular account name. Do not use
your regular account password

EDIT: migth also be mandatory to disable two factor authentification