mail keeps asking for password

Delete the password from Keychain Access.

I just found an article about how to respond to the "account already exists" message. I turned off iCloud and then connected to my email. Everything worked fine and I downloaded all the mail that had been hung up. Then I turned iCloud back on. I'm hoping that fixed everything.

If Mail on your Mac keeps asking for your password

This article is useless. I just experienced a Mail crash on my computer. When I restarted, all of a sudden Mail won't connect to my email provider with the account name and password it was using successfully before the crash. Now I keep getting the "unable to verify account name and password" message when I try to go online with the account. This is the second time I'm encountering this issue in the past 10 days, and last time I totally reloaded my system software. I am hoping not to have to do that again.

The password that displays when I go to Keychain Access App and look at the mail password is not the correct password.

OK, I deleted the password from Keychain. Now the message I get when I try to sign onto my email with my email provider's password is "this account already exists." Since I'm not trying to create a new account, only sign on to an existing one, this message makes no sense.

Since you found your own solution, you should post what the solution was or a link to the solution. This is to help others who may have the same problem as you.

Here's the link to the article that provided that solution to this issue. Although the solution says it's for El Capitan, it worked for me and I'm using High Sierra:

http://solutionowl.com/mac-mail-account-already-exists-capitan/

If you supply the password, does it work? Try going to Applications/Utilities/Keychain Access and delete and email password there.