Yahoo users need to authenticate using an app password instead of their email password.
To generate an app password:
- Sign in to Yahoo Mail.
- Navigate to Account Info.
- Go to the Account security settings.
- At the bottom of the page, choose the option to Generate app password or Manage app passwords.
- Generate a new app password.
- Use the new password to try authenticating with Nylas.
These steps will also work for users who have two-factor authentication enabled.
For more details, read the generate third-party app passwords article from Yahoo.