cannot get Mail to accept my yahoo account user name and password.

If this is the same problem I had, there is an easy fix.  DO NOT delete your account until you try this… you will lose all of

your saved emails (including sent and trash). Instead, just fix your existing preferences (explained below).

Symptom:  Apple Mail application suddenly does not recognize your Yahoo log in username or password that you know is correct, and it will not download or send mail from your Mac.  OR it claims there is a server error and to try again later, leaving your account offline. This could be due to an issue between Yahoo and “third-party apps”. 

Solution:  Create a temporary (disposable) password with Yahoo and add it to the Mail preferences.  You only need to do this once because “Mail” doesn’t ask you for this information again… it just stores and uses it.

(If you don’t want to follow my instructions below, you can find the yahoo help info at https://help.yahoo.com/kb/generate-third-party-passwords-sln15241.html)

Go to your online Yahoo email page and Sign in to your account security page:

Hover your cursor over your name in the upper right hand area and select “Account Info”. Then select “Account Security” (you may have to sign in to Yahoo again -- https://login.yahoo.com/account/security.) Select “Generate app password or Manage app passwords”.  Select “Mac Mail” (or other 3rd party app in trouble) and click on “Generate.” 

Now, COPY the temporary password (that is disposable and won’t be used again).

Go to your Mac Mail app preferences:

With “Mail” app open, go to the Mail Preferences (under “Mail” next to the apple in the upper left corner of your screen).  In preferences, select “Accounts” from the top line, and make sure you have the Yahoo email account selected in the left

hand side bar.  Choose “Server Settings”. 

Now PASTE the temporary password into the two places that ask for a password, Incoming and Outgoing Mail Servers.

Remember to “Save” at the bottom of the window.  Close this Mail preferences window.

Go back to Yahoo and close the window there, too.

Now, try to send / receive mail on your Mac and see if that works for you.  Good luck!!

Had the same issue with my SBCGLOBAL.net account which is Yahoo. Changed the password to utilize some other features of Yahoo, and then could not receive mail after updating to the new password in my preferences. Apple support tried to help me with over 40 minutes on a call with no luck. Suggested calling ATT for help. Finally got some support from ATT regarding this after four different calls. There is a Secure Mail Key that you have to use to set up the account in Apple Mail. This Mail Key is set up through the ATT website that you can log into as a user of one of their email services (Yahoo, Bellsouth, SBCGlobal, etc) and create. Call ATT at 800-288-2020 and ask for Tech Support in the automated system. They were on the phone with me for almost an hour but we got all my devices to receive mail again. Hope this helps someone!

Yes, but realize that your problem has nothing to do with the internet service provider. Mine is Comcast. ATT is the provider of yahoo accounts. They are who you need to talk to.

Me too. Just stopped working in last 48 hrs.

Email on iphone works, access to yahoo via webmail works. removed and installed several times.

Still refusing to verify.