Yahoo

Needs preparation.

To use Delta Chat with your Yahoo email address you have to allow “less secure apps”:

In your account security screen you will find a setting titled “Allow apps that use less secure sign in”. Please switch that on to allow Delta Chat to log in to your account.

Don’t be afraid: “less secure sign in” sounds bad, but it isn’t. The wording deliberately tries to scare you away because Yahoo wants you to only use their own apps.