Why Yahoo rejects your normal password
Yahoo does not accept your everyday password from outside mail apps. Instead you create an app password, a code that Yahoo generates for one app. The mail app sends that code in place of your password. If you enter your regular Yahoo password there, the sign in fails with an error that looks like a wrong password.
What can break an app password that worked before
An app password stops working if you delete it from your Yahoo account, or if you generate a replacement that cancels the old code. If you change security settings on the account, it is worth making a fresh one. Yahoo shows the code only once, so a code copied with a missing character is refused too.
The message is vague on purpose
Mail apps often show the same generic message for a wrong password, an expired app password and a blocked sign in. That is why the error looks like your password is wrong when the real problem is the type of password.
The fix: make a Yahoo app password
- Sign in to your Yahoo account and open Account Security.
- Choose Generate app password (or Manage app passwords) and create one named Curo.
- Copy the code Yahoo shows you. You only see it once.
- In Curo, add a mailbox and type your Yahoo address. Curo recognises Yahoo and fills in the server settings for you.
- Paste the code into the app password box and click Connect and sync.