Yahoo users need to authenticate using an app password instead of their email password.
To generate an app password:
Go to the "Account security" settings in "Account Info"
At the bottom of the page, choose the option to "Generate app password" or "Manage app passwords".
Generate a new app password.
Copy that password to your clipboard.
Try authenticating again with Navigate, using the newly-generated password.
Note: We recommend using a password manager like Dashlane or 1Password. Cyrano will never see it, and Yahoo will NOT display this password again. If you lose this password, you will need to create a new password again.
This approach is also appropriate for users who have two-factor authentication enabled.
For more details, see Generate third-party app passwords in Yahoo Help.