Mail Problem....please help?

[N4CQD]

I'm having problems with Mail on my iMac.
AT&T (Bellsouth - Yahoo)is my server. I am unable to receive email using Mail. Until two days ago, it worked fine, for years, but since then, it keeps giving me an error message that my PW is incorrect. I havent changed my PW in years, so I know it isn't incorrect. Ive removed and re-installed my account information on Preferences several times, still doesn't work. Ive been on the telephone with Yahoo Tech Support, still doesn't work. Ive had my iMac to the Genius Bar at The Apple Store, still doesn't work.
The Inbox on Mail shows a (~), I click on it to put all accounts on line, no change. Still doesn't work.
I'm able to log onto my email account through the Yahoo Web Site, using my current PW, and it works, showing me all of my emails. No problems.
Any ideas as to how I can get Mail to work?
Would appreciate any help.

Update May 21, 6pm:
Late last night, I went to Mail, and found 17 emails waiting for me, and I thought the issue had resolved. Well, this afternoon, after opening Mail, here we go again.....an error message asking me for my PW over and over and over again. A (~) in my Inbox, and cannot receive any emails. What a joke!
This is definitely a Yahoo issue!
I cant say for sure whether this is a Yahoo issue with Apple Computer software or if Microsoft computers suffer the same problems with their email apps. But in the past few days, I have seen so many of the exact same complaints about Yahoo from Mail users here on this forum, it isn't just me.

 

[gc916]

This is just a wild guess...have you recently enabled two-factor authentication on your Yahoo Mail account?

 

[MisterMe]

...
Would appreciate any help.

Quite a number of Yahoo! Mail users have problems with the service, particularly if accessing it via Mail. The symptoms experienced by most users is that Yahoo! repeatedly demands that the user reenter the account password. Yahoo! Mail is very popular among students. I have noticed for a number of years that some of my students experience similar issues as yours with attachments. And they use the Yahoo! webmail client in their browsers and rather than a standalone email client.

 

[mic j]

I finally gave up on Yahoo Mail and moved to GMail. Yahoo Mail became a total headache of the last few months (worked very well before that), constantly requiring my password. I was really concerned about how hard it would be to change all of my contacts to a new mail address. It really turned out not to be as bad as I thought. Sent an change of address to everyone in my Address Book and changed address with a handful of commercial places/websites. Then I just took my Yahoo Mail offline (I did not remove it or shut it down with Yahoo). Once a day, I take it back online and check for any email from places I missed. There have been only a handful and now I am pretty much just receiving ads and Viagra/call girl/designer watch/sex toy offers. Oh...and did I mention, a nice guy from Nigeria that wants me to give him my bank info. Still thinking about that one!!

Also, each time I take the Yahoo Mail back online, I don't have to enter a password...interesting.

GMail has been working flawlessly.