I am currently running KMail 4.14.4 in KDE Frameworks 5.7 I've added my Yahoo Account to KMail, but for some reason the inbox folder will only retrieve messages from 2013 and nothing newer. Other folders retrieve all messages. Not sure what or why this is happening.

Can you check if anything is printed in the terminal? Run "akonadictl restart" there, and attempt a sync, see if there are debug messages that help diagnosing the problem.

I just can't login with my credentials utilizing the following adresses (everything is according to yahoo's help guide):

-IMAP Server: imap.mail.yahoo.com
SSL port 993
-SMTP server: smtp.mail.yahoo.com
SSL port 465

Error message: A000002 NO AUTHENTICATE Invalid credentials [ AUTHENTICATIONFAILED ]

What would be the problem?

Suggest me how to fix yahoo 404 HTTP error, I couldn't understand I tried all the remedies to fix it. still not able to visit, I checked URL, retype it, reload the page but couldn't fix it.